A classification thus formed is properly scientific or philosophical,

and is commonly called a Natural, in contradistinction to a Technical

or Artificial, classification or arrangement. The phrase Natural

Classification seems most peculiarly appropriate to such arrangements as

correspond, in the groups which they form, to the spontaneous tendencies

of the mind, by placing together the objects most similar in their

general aspect: in opposition to those technical systems which,

arranging things according to their agreement in some circumstance

arbitrarily selected, often throw into the same group objects which in

the general aggregate of their properties present no resemblance, and

into different and remote groups, others which have the closest

similarity. It is one of the most valid recommendations of any

classification to the character of a scientific one, that it shall be a

natural classification in this sense also; for the test of its

scientific character is the number and importance of the properties

which can be asserted in common of all objects included in a group; and

properties on which the general aspect of the things depends, are, if

only on that ground, important, as well as, in most cases, numerous.

But, though a strong recommendation, this circumstance is not a _sine

quâ non_; since the most obvious properties of things may be of trifling

importance compared with others that are not obvious. I have seen it

mentioned as a great absurdity in the Linnæan classification, that it

places (which by the way it does not) the violet by the side of the oak:

it certainly dissevers natural affinities, and brings together things

quite as unlike as the oak and the violet are. But the difference,

apparently so wide, which renders the juxtaposition of those two

vegetables so suitable an illustration of a bad arrangement, depends, to

the common eye, mainly on mere size and texture; now if we made it our

study to adopt the classification which would involve the least peril of

similar _rapprochements_, we should return to the obsolete division into

trees, shrubs, and herbs, which though of primary importance with regard

to more general aspect, yet (compared even with so petty and unobvious a

distinction as that into dicotyledons and monocotyledons) answers to so

few differences in the other properties of plants, that a classification

founded on it (independently of the indistinctness of the lines of

demarcation) would be as completely artificial and technical as the

Linnæan.

Our natural groups, therefore, must often be founded not on the obvious,

but on the unobvious properties of things, when these are of greater

importance. But in such cases it is essential that there should be some

other property or set of properties, more readily recognisable by the

observer, which coexist with, and may be received as marks of, the

properties which are the real groundwork of the classification. A

natural arrangement, for example, of animals, must be founded in the

main on their internal structure, but (as has been justly remarked) it

would be absurd that we should not be able to determine the genus and

species of an animal without first killing it. On this ground, the

preference, among zoological classifications, is probably due to that of

M. de Blainville, founded on the differences in the external

integuments; differences which correspond, much more accurately than

might be supposed, to the really important varieties, both in the other

parts of the structure, and in the habits and history of the animals.

This shows, more strongly than ever, how extensive a knowledge of the

properties of objects is necessary for making a good classification of

them. And as it is one of the uses of such a classification that by

drawing attention to the properties on which it is founded, and which if

the classification be good are marks of many others, it facilitates the

discovery of those others; we see in what manner our knowledge of

things, and our classification of them, tend mutually and indefinitely

to the improvement of each other.

We said just now that the classification of objects should follow those

of their properties which indicate not only the most numerous, but also

the most important peculiarities. What is here meant by importance? It

has reference to the particular end in view; and the same objects,

therefore, may admit with propriety of several different

classifications. Each science or art forms its classification of things

according to the properties which fall within its special cognizance, or

of which it must take account in order to accomplish its peculiar

practical end. A farmer does not divide plants, like a botanist, into

dicotyledonous and monocotyledonous, but into useful plants and weeds. A

geologist divides fossils, not like a zoologist, into families

corresponding to those of living species, but into fossils of the

secondary and of the tertiary periods, above the coal and below the

coal, &c. Whales are or are not fish, according to the purpose for which

we are considering them. "If we are speaking of the internal structure

and physiology of the animal, we must not call them fish; for in these

respects they deviate widely from fishes: they have warm blood, and

produce and suckle their young as land quadrupeds do. But this would not

prevent our speaking of the _whale fishery_, and calling such animals

_fish_ on all occasions connected with this employment; for the

relations thus rising depend upon the animal's living in the water, and

being caught in a manner similar to other fishes. A plea that human laws

which mention fish do not apply to whales, would be rejected at once by

an intelligent judge."[19]

These different classifications are all good, for the purposes of their

own particular departments of knowledge or practice. But when we are

studying objects not for any special practical end, but for the sake of

extending our knowledge of the whole of their properties and relations,

we must consider as the most important attributes, those which

contribute most, either by themselves or by their effects, to render the

things like one another, and unlike other things; which give to the

class composed of them the most marked individuality; which fill, as it

were, the largest space in their existence, and would most impress the

attention of a spectator who knew all their properties but was not

specially interested in any. Classes formed on this principle may be

called, in a more emphatic manner than any others, natural groups.

§ 3. On the subject of these groups Dr. Whewell lays down a theory,

grounded on an important truth, which he has, in some respects,

expressed and illustrated very felicitously; but also, as it appears to

me, with some admixture of error. It will be advantageous, for both

these reasons, to extract the statement of his doctrine in the very

words he has used.

"Natural groups," according to this theory,[20] are "given by Type, not

by Definition." And this consideration accounts for that "indefiniteness

and indecision which we frequently find in the descriptions of such

groups, and which must appear so strange and inconsistent to any one who

does not suppose these descriptions to assume any deeper ground of

connexion than an arbitrary choice of the botanist. Thus in the family

of the rose-tree, we are told that the _ovules_ are _very rarely_ erect,

the _stigmata usually_ simple. Of what use, it might be asked, can such

loose accounts be? To which the answer is, that they are not inserted in

order to distinguish the species, but in order to describe the family,

and the total relations of the ovules and the stigmata of the family are

better known by this general statement. A similar observation may be

made with regard to the Anomalies of each group, which occur so

commonly, that Mr. Lindley, in his _Introduction to the Natural System

of Botany_, makes the 'Anomalies' an article in each family. Thus, part

of the character of the Rosaceæ is, that they have alternate _stipulate_

leaves, and that the _albumen_ is _obliterated_; but yet in _Lowea_, one

of the genera of this family, the stipulæ are _absent_; and the albumen

is _present_ in another, _Neillia_. This implies, as we have already

seen, that the artificial character (or _diagnosis_, as Mr. Lindley

calls it,) is imperfect. It is, though very nearly, yet not exactly,

commensurate with the natural group: and hence in certain cases this

character is made to yield to the general weight of natural affinities.

"These views,--of classes determined by characters which cannot be

expressed in words,--of propositions which state, not what happens in

all cases, but only usually,--of particulars which are included in a

class, though they transgress the definition of it, may probably

surprise the reader. They are so contrary to many of the received

opinions respecting the use of definitions, and the nature of scientific

propositions, that they will probably appear to many persons highly

illogical and unphilosophical. But a disposition to such a judgment

arises in a great measure from this, that the mathematical and

mathematico-physical sciences have, in a great degree, determined men's

views of the general nature and form of scientific truth; while Natural

History has not yet had time or opportunity to exert its due influence

upon the current habits of philosophizing. The apparent indefiniteness

and inconsistency of the classifications and definitions of Natural

History belongs, in a far higher degree, to all other except

mathematical speculations; and the modes in which approximations to

exact distinctions and general truths have been made in Natural History,

may be worthy our attention, even for the light they throw upon the best

modes of pursuing truth of all kinds.

"Though in a Natural group of objects a definition can no longer be of

any use as a regulative principle, classes are not therefore left quite

loose, without any certain standard or guide. The class is steadily

fixed, though not precisely limited; it is given, though not

circumscribed; it is determined, not by a boundary line without, but by

a central point within; not by what it strictly excludes, but by what it

eminently includes; by an example, not by a precept; in short, instead

of a Definition we have a Type for our director.

"A Type is an example of any class, for instance a species of a genus,

which is considered as eminently possessing the character of the class.

All the species which have a greater affinity with this type-species

than with any others, form the genus, and are arranged about it,

deviating from it in various directions and different degrees. Thus a

genus may consist of several species which approach very near the type,

and of which the claim to a place with it is obvious; while there may be

other species which straggle further from this central knot, and which

yet are clearly more connected with it than with any other. And even if

there should be some species of which the place is dubious, and which

appear to be equally bound to two generic types, it is easily seen that

this would not destroy the reality of the generic groups, any more than

the scattered trees of the intervening plain prevent our speaking

intelligibly of the distinct forests of two separate hills.

"The type-species of every genus, the type-genus of every family, is,

then, one which possesses all the characters and properties of the genus

in a marked and prominent manner. The type of the Rose family has

alternate stipulate leaves, wants the albumen, has the ovules not erect,

has the stigmata simple, and besides these features, which distinguish

it from the exceptions or varieties of its class, it has the features

which make it prominent in its class. It is one of those which possess

clearly several leading attributes; and thus, though we cannot say of

any one genus that it _must_ be the type of the family, or of any one

species that it _must_ be the type of the genus, we are still not wholly

to seek; the type must be connected by many affinities with most of the

others of its group; it must be near the centre of the crowd, and not

one of the stragglers."

In this passage (the latter part of which especially I cannot help

noticing as an admirable example of philosophic style) Dr. Whewell has

stated very clearly and forcibly, but (I think) without making all

necessary distinctions, one of the principles of a Natural

Classification. What this principle is, what are its limits, and in what

manner he seems to me to have overstepped them, will appear when we have

laid down another rule of Natural Arrangement, which appears to me still

more fundamental.

§ 4. The reader is by this time familiar with the general truth (which I

restate so often on account of the great confusion in which it is

commonly involved), that there are in nature distinctions of Kind;

distinctions not consisting in a given number of definite properties,

_plus_ the effects which follow from those properties, but running

through the whole nature, through the attributes generally, of the

things so distinguished. Our knowledge of the properties of a Kind is

never complete. We are always discovering, and expecting to discover,

new ones. Where the distinction between two classes of things is not one

of Kind, we expect to find their properties alike, except where there is

some reason for their being different. On the contrary, when the

distinction is in Kind, we expect to find the properties different

unless there be some cause for their being the same. All knowledge of a

Kind must be obtained by observation and experiment upon the Kind

itself; no inference respecting its properties from the properties of

things not connected with it by Kind, goes for more than the sort of

presumption usually characterized as an analogy, and generally in one of

its fainter degrees.

Since the common properties of a true Kind, and consequently the general

assertions which can be made respecting it, or which are certain to be

made hereafter as our knowledge extends, are indefinite and

inexhaustible; and since the very first principle of natural

classification is that of forming the classes so that the objects

composing each may have the greatest number of properties in common;

this principle prescribes that every such classification shall recognise

and adopt into itself all distinctions of Kind, which exist among the

objects it professes to classify. To pass over any distinctions of Kind,

and substitute definite distinctions, which, however considerable they

may be, do not point to ulterior unknown differences, would be to

replace classes with more by classes with fewer attributes in common;

and would be subversive of the Natural Method of Classification.

Accordingly all natural arrangements, whether the reality of the

distinction of Kinds was felt or not by their framers, have been led, by

the mere pursuit of their own proper end, to conform themselves to the

distinctions of Kind, so far as these had been ascertained at the time.

The Species of Plants are not only real Kinds, but are probably,[21]

all of them, real lowest Kinds, Infimæ Species; which if we were to

subdivide, as of course it is open to us to do, into subclasses, the

subdivision would necessarily be founded on _definite_ distinctions, not

pointing (apart from what may be known of their causes or effects) to

any difference beyond themselves.

In so far as a natural classification is grounded on real Kinds, its

groups are certainly not conventional; it is perfectly true that they do

not depend upon an arbitrary choice of the naturalist. But it does not

follow, nor, I conceive, is it true, that these classes are determined

by a type, and not by characters. To determine them by a type would be

as sure a way of missing the Kind, as if we were to select a set of

characters arbitrarily. They are determined by characters, but these are

not arbitrary. The problem is, to find a few definite characters which

point to the multitude of indefinite ones. Kinds are Classes between

which there is an impassable barrier; and what we have to seek is, marks

whereby we may determine on which side of the barrier an object takes

its place. The characters which will best do this should be chosen: if

they are also important in themselves, so much the better. When we have

selected the characters, we parcel out the objects according to those

characters, and not, I conceive, according to resemblance to a type. We

do not compose the species Ranunculus acris, of all plants which bear a

satisfactory degree of resemblance to a model-buttercup, but of those

which possess certain characters selected as marks by which we might

recognise the possibility of a common parentage; and the enumeration of

those characters is the definition of the species.

The question next arises, whether, as all Kinds must have a place among

the classes, so all the classes in a natural arrangement must be Kinds?

And to this I answer, certainly not. The distinctions of Kinds are not

numerous enough to make up the whole of a classification. Very few of

the genera of plants, or even of the families, can be pronounced with

certainty to be Kinds. The great distinctions of Vascular and Cellular,

Dicotyledonous or Exogenous and Monocotyledonous or Endogenous plants,

are perhaps differences of Kind; the lines of demarcation which divide

those classes seem (though even on this I would not pronounce

positively) to go through the whole nature of the plants. But the

different species of a genus, or genera of a family, usually have in

common only a limited number of characters. A Rose does not seem to

differ from a Rubus, or the Umbelliferæ from the Ranunculaceæ, in much

else than the characters botanically assigned to those genera or those

families. Unenumerated differences certainly do exist in some cases;

there are families of plants which have peculiarities of chemical

composition, or yield products having peculiar effects on the animal

economy. The Cruciferæ and Fungi contain an unusual proportion of

nitrogen; the Labiatæ are the chief sources of essential oils, the

Solaneæ are very commonly narcotic, &c. In these and similar cases there

are possibly distinctions of Kind; but it is by no means indispensable

that there should be. Genera and Families may be eminently natural,

though marked out from one another by properties limited in number;

provided those properties are important, and the objects contained in

each genus or family resemble each other more than they resemble

anything which is excluded from the genus or family.

After the recognition and definition, then, of the _infimæ species_, the

next step is to arrange those _infimæ species_ into larger groups:

making these groups correspond to Kinds wherever it is possible, but in

most cases without any such guidance. And in doing this it is true that

we are naturally and properly guided, in most cases at least, by

resemblance to a type. We form our groups round certain selected Kinds,

each of which serves as a sort of exemplar of its group. But though the

groups are suggested by types, I cannot think that a group when formed

is _determined_ by the type; that in deciding whether a species belongs

to the group, a reference is made to the type, and not to the

characters; that the characters "cannot be expressed in words." This

assertion is inconsistent with Dr. Whewell's own statement of the

fundamental principle of classification, namely, that "general

assertions shall be possible." If the class did not possess any

characters in common, what general assertions would be possible

respecting it? Except that they all resemble each other more than they

resemble anything else, nothing whatever could be predicated of the

class.

The truth is, on the contrary, that every genus or family is framed with

distinct reference to certain characters, and is composed, first and

principally, of species which agree in possessing all those characters.

To these are added, as a sort of appendix, such other species, generally

in small number, as possess _nearly_ all the properties selected;

wanting some of them one property, some another, and which, while they

agree with the rest _almost_ as much as these agree with one another, do

not resemble in an equal degree any other group. Our conception of the

class continues to be grounded on the characters; and the class might be

defined, those things which _either_ possess that set of characters,

_or_ resemble the things that do so, more than they resemble anything

else.

And this resemblance itself is not, like resemblance between simple

sensations, an ultimate fact, unsusceptible of analysis. Even the

inferior degree of resemblance is created by the possession of common

characters. Whatever resembles the genus Rose more than it resembles any

other genus, does so because it possesses a greater number of the

characters of that genus, than of the characters of any other genus. Nor

can there be any real difficulty in representing, by an enumeration of

characters, the nature and degree of the resemblance which is strictly

sufficient to include any object in the class. There are always some

properties common to all things which are included. Others there often

are, to which some things, which are nevertheless included, are

exceptions. But the objects which are exceptions to one character are

not exceptions to another: the resemblance which fails in some

particulars must be made up for in others. The class, therefore, is

constituted by the possession of _all_ the characters which are

universal, and _most_ of those which admit of exceptions. If a plant had

the ovules erect, the stigmata divided, possessed the albumen, and was

without stipules, it possibly would not be classed among the Rosaceæ.

But it may want any one, or more than one of those characters, and not

be excluded. The ends of a scientific classification are better answered

by including it. Since it agrees so nearly, in its known properties,

with the sum of the characters of the class, it is likely to resemble

that class more than any other in those of its properties which are

still undiscovered.

Not only, therefore, are natural groups, no less than any artificial

classes, determined by characters; they are constituted in contemplation

of, and by reason of, characters. But it is in contemplation not of

those characters only which are rigorously common to all the objects

included in the group, but of the entire body of characters, all of

which are found in most of those objects, and most of them in all. And

hence our conception of the class, the image in our minds which is

representative of it, is that of a specimen complete in all the

characters; most naturally a specimen which, by possessing them all in

the greatest degree in which they are ever found, is the best fitted to

exhibit clearly, and in a marked manner, what they are. It is by a

mental reference to this standard, not instead of, but in illustration

of, the definition of the class, that we usually and advantageously

determine whether any individual or species belongs to the class or not.

And this, as it seems to me, is the amount of truth contained in the

doctrine of Types.

We shall see presently that where the classification is made for the

express purpose of a special inductive inquiry, it is not optional, but

necessary for fulfilling the conditions of a correct Inductive Method,

that we should establish a type-species or genus, namely, the one which

exhibits in the most eminent degree the particular phenomenon under

investigation. But of this hereafter. It remains, for completing the

theory of natural groups, that a few words should be said on the

principles of the nomenclature adapted to them.

§ 5. A Nomenclature in science, is, as we have said, a system of the

names of Kinds. These names, like other class-names, are defined by the

enumeration of the characters distinctive of the class. The only merit

which a set of names can have beyond this, is to convey, by the mode of

their construction, as much information as possible: so that a person

who knows the thing, may receive all the assistance which the name can

give in remembering what he knows, while he who knows it not, may

receive as much knowledge respecting it as the case admits of, by merely

being told its name.

There are two modes of giving to the name of a Kind this sort of

significance. The best, but which unfortunately is seldom practicable,

is when the word can be made to indicate, by its formation, the very

properties which it is designed to connote. The name of a Kind does not,

of course, connote all the properties of the Kind, since these are

inexhaustible, but such of them as are sufficient to distinguish it;

such as are sure marks of all the rest. Now, it is very rarely that one

property, or even any two or three properties, can answer this purpose.

To distinguish the common daisy from all other species of plants would

require the specification of many characters. And a name cannot, without

being too cumbrous for use, give indication, by its etymology or mode of

construction, of more than a very small number of these. The

possibility, therefore, of an ideally perfect Nomenclature, is probably

confined to the one case in which we are happily in possession of

something nearly approaching to it; the Nomenclature of elementary

Chemistry. The substances, whether simple or compound, with which

chemistry is conversant, are Kinds, and, as such, the properties which

distinguish each of them from the rest are innumerable; but in the case

of compound substances (the simple ones are not numerous enough to

require a systematic nomenclature), there is one property, the chemical

composition, which is of itself sufficient to distinguish the Kind; and

is (with certain reservations not yet thoroughly understood) a sure mark

of all the other properties of the compound. All that was needful,

therefore, was to make the name of every compound express, on the first

hearing, its chemical composition; that is, to form the name of the

compound, in some uniform manner, from the names of the simple

substances which enter into it as elements. This was done, most

skilfully and successfully, by the French chemists. The only thing left

unexpressed by them was the exact proportion in which the elements were

combined; and even this, since the establishment of the atomic theory,

it has been found possible to express by a simple adaptation of their

phraseology.

But where the characters which must be taken into consideration in order

sufficiently to designate the Kind, are too numerous to be all signified

in the derivation of the name, and where no one of them is of such

preponderant importance as to justify its being singled out to be so

indicated, we may avail ourselves of a subsidiary resource. Though we

cannot indicate the distinctive properties of the Kind, we may indicate

its nearest natural affinities, by incorporating into its name the name

of the proximate natural group of which it is one of the species. On

this principle is founded the admirable binary nomenclature of botany

and zoology. In this nomenclature the name of every species consists of

the name of the genus, or natural group next above it, with a word added

to distinguish the particular species. The last portion of the compound

name is sometimes taken from some _one_ of the peculiarities in which

that species differs from others of the genus; as Clematis

_integrifolia_, Potentilla _alba_, Viola _palustris_, Artemisia

_vulgaris_; sometimes from a circumstance of an historical nature, as

Narcissus _poeticus_, Potentilla _tormentilla_ (indicating that the

plant was formerly known by the latter name), Exacum _Candollii_ (from

the fact that De Candolle was its first discoverer); and sometimes the

word is purely conventional, as Thlaspi _bursa-pastoris_, Ranunculus

_thora_; it is of little consequence which; since the second, or as it

is usually called, the specific name, could at most express,

independently of convention, no more than a very small portion of the

connotation of the term. But by adding to this the name of the superior

genus, we may make the best amends we can for the impossibility of so

contriving the name as to express all the distinctive characters of the

Kind. We make it, at all events, express as many of those characters as

are common to the proximate natural group in which the Kind is included.

If even those common characters are so numerous or so little familiar as

to require a further extension of the same resource, we might, instead

of a binary, adopt a ternary nomenclature, employing not only the name

of the genus, but that of the next natural group in order of generality

above the genus, commonly called the Family. This was done in the

mineralogical nomenclature proposed by Professor Mohs. "The names framed

by him were not composed of two, but of three elements, designating

respectively the Species, the Genus, and the Order; thus he has such

species as _Rhombohedral Lime Haloide_, _Octohedral Fluor Haloide_,

_Prismatic Hal Baryte_."[22] The binary construction, however, has been

found sufficient in botany and zoology, the only sciences in which this

general principle has hitherto been successfully adopted in the

construction of a nomenclature.

Besides the advantage which this principle of nomenclature possesses, in

giving to the names of species the greatest quantity of independent

significance which the circumstances of the case admit of, it answers

the further end of immensely economizing the use of names, and

preventing an otherwise intolerable burden on the memory. When the names

of species become extremely numerous, some artifice (as Dr. Whewell[23]

observes) becomes absolutely necessary to make it possible to recollect

or apply them. "The known species of plants, for example, were ten

thousand in the time of Linnæus, and are now probably sixty thousand. It

would be useless to endeavour to frame and employ separate names for

each of these species. The division of the objects into a subordinated

system of classification enables us to introduce a Nomenclature which

does not require this enormous number of names. Each of the genera has

its name, and the species are marked by the addition of some epithet to

the name of the genus. In this manner about seventeen hundred generic

names, with a moderate number of specific names, were found by Linnæus

sufficient to designate with precision all the species of vegetables

known at his time." And though the number of generic names has since

greatly increased, it has not increased in anything like the proportion

of the multiplication of known species.

CHAPTER VIII.

OF CLASSIFICATION BY SERIES.

§ 1. Thus far, we have considered the principles of scientific

classification so far only as relates to the formation of natural

groups; and at this point most of those who have attempted a theory of

natural arrangement, including, among the rest, Dr. Whewell, have

stopped. There remains, however, another, and a not less important

portion of the theory, which has not yet, as far as I am aware, been

systematically treated of by any writer except M. Comte. This is, the

arrangement of the natural groups into a natural series.[24]

The end of Classification, as an instrument for the investigation of

nature, is (as before stated) to make us think of those objects

together, which have the greatest number of important common properties;

and which therefore we have oftenest occasion, in the course of our

inductions, for taking into joint consideration. Our ideas of objects

are thus brought into the order most conducive to the successful

prosecution of inductive inquiries generally. But when the purpose is to

facilitate some particular inductive inquiry, more is required. To be

instrumental to that purpose, the classification must bring those

objects together, the simultaneous contemplation of which is likely to

throw most light upon the particular subject. That subject being the

laws of some phenomenon or some set of connected phenomena; the very

phenomenon or set of phenomena in question must be chosen as the

groundwork of the classification.

The requisites of a classification intended to facilitate the study of a

particular phenomenon, are, first, to bring into one class all Kinds of

things which exhibit that phenomenon, in whatever variety of forms or

degrees; and secondly, to arrange those Kinds in a series according to

the degree in which they exhibit it, beginning with those which exhibit

most of it, and terminating with those which exhibit least. The

principal example, as yet, of such a classification, is afforded by

comparative anatomy and physiology, from which, therefore, our

illustrations shall be taken.

§ 2. The object being supposed to be, the investigation of the laws of

animal life; the first step, after forming the most distinct conception

of the phenomenon itself, possible in the existing state of our

knowledge, is to erect into one great class (that of animals) all the

known Kinds of beings where that phenomenon presents itself; in however

various combinations with other properties, and in however different

degrees. As some of these Kinds manifest the general phenomenon of

animal life in a very high degree, and others in an insignificant

degree, barely sufficient for recognition; we must, in the next place,

arrange the various Kinds in a series, following one another according

to the degrees in which they severally exhibit the phenomenon; beginning

therefore with man, and ending with the most imperfect kinds of

zoophytes.

This is merely saying that we should put the instances, from which the

law is to be inductively collected, into the order which is implied in

one of the four Methods of Experimental Inquiry discussed in the

preceding Book; the fourth Method, that of Concomitant Variations. As

formerly remarked, this is often the only method to which recourse can

be had, with assurance of a true conclusion, in cases in which we have

but limited means of effecting, by artificial experiments, a separation

of circumstances usually conjoined. The principle of the method is, that

facts which increase or diminish together, and disappear together, are

either cause and effect, or effects of a common cause. When it has been

ascertained that this relation really subsists between the variations, a

connexion between the facts themselves may be confidently laid down,

either as a law of nature or only as an empirical law, according to

circumstances.

That the application of this Method must be preceded by the formation of

such a series as we have described, is too obvious to need being pointed

out; and the mere arrangement of a set of objects in a series, according

to the degrees in which they exhibit some fact of which we are seeking

the law, is too naturally suggested by the necessities of our inductive

operations, to require any lengthened illustration here. But there are

cases in which the arrangement required for the special purpose, becomes

the determining principle of the classification of the same objects for

general purposes. This will naturally and properly happen, when those

laws of the objects which are sought in the special inquiry enact so

principal a part in the general character and history of those

objects--exercise so much influence in determining all the phenomena of

which they are either the agents or the theatre--that all other

differences existing among the objects are fittingly regarded as mere

modifications of the one phenomenon sought; effects determined by the

co-operation of some incidental circumstance with the laws of that

phenomenon. Thus in the case of animated beings, the differences between

one class of animals and another may reasonably be considered as mere

modifications of the general phenomenon, animal life; modifications

arising either from the different degrees in which that phenomenon is

manifested in different animals, or from the intermixture of the effects

of incidental causes peculiar to the nature of each, with the effects

produced by the general laws of life; those laws still exercising a

predominant influence over the result. Such being the case, no other

inductive inquiry respecting animals can be successfully carried on,

except in subordination to the great inquiry into the universal laws of

animal life. And the classification of animals best suited to that one

purpose, is the most suitable to all the other purposes of zoological

science.

§ 3. To establish a classification of this sort, or even to apprehend it

when established, requires the power of recognising the essential

similarity of a phenomenon, in its minuter degrees and obscurer forms,

with what is called the _same_ phenomenon in the greatest perfection of

its development; that is, of identifying with each other all phenomena

which differ only in degree, and in properties which we suppose to be

caused by difference of degree. In order to recognise this identity, or

in other words, this exact similarity of quality, the assumption of a

type-species is indispensable. We must consider as the type of the

class, that among the Kinds included in it, which exhibits the

properties constitutive of the class, in the highest degree; conceiving

the other varieties as instances of degeneracy, as it were, from that

type; deviations from it by inferior intensity of the characteristic

property or properties. For every phenomenon is best studied (_cæteris

paribus_) where it exists in the greatest intensity. It is there that

the effects which either depend on it, or depend on the same causes with

it, will also exist in the greatest degree. It is there, consequently,

and only there, that those effects of it, or joint effects with it, can

become fully known to us, so that we may learn to recognise their

smaller degrees, or even their mere rudiments, in cases in which the

direct study would have been difficult or even impossible. Not to

mention that the phenomenon in its higher degrees may be attended by

effects or collateral circumstances which in its smaller degrees do not

occur at all, requiring for their production in any sensible amount a

greater degree of intensity of the cause than is there met with. In man,

for example, (the species in which both the phenomenon of animal and

that of organic life exist in the highest degree,) many subordinate

phenomena develop themselves in the course of his animated existence,

which the inferior varieties of animals do not show. The knowledge of

these properties may nevertheless be of great avail towards the

discovery of the conditions and laws of the general phenomenon of life,

which is common to man with those inferior animals. And they are, even,

rightly considered as properties of animated nature itself; because they

may evidently be affiliated to the general laws of animated nature;

because we may fairly presume that some rudiments or feeble degrees of

those properties would be recognised in all animals by more perfect

organs, or even by more perfect instruments, than ours; and because

those may be correctly termed properties of a class, which a thing

exhibits exactly in proportion as it belongs to the class, that is, in

proportion as it possesses the main attributes constitutive of the

class.

§ 4. It remains to consider how the internal distribution of the series

may most properly take place: in what manner it should be divided into

Orders, Families, and Genera.

The main principle of division must of course be natural affinity; the

classes formed must be natural groups: and the formation of these has

already been sufficiently treated of. But the principles of natural

grouping must be applied in subordination to the principle of a natural

series. The groups must not be so constituted as to place in the same

group things which ought to occupy different points of the general

scale. The precaution necessary to be observed for this purpose is, that

the _primary_ divisions must be grounded not on all distinctions

indiscriminately, but on those which correspond to variations in the

degree of the main phenomenon. The series of Animated Nature should be

broken into parts at the points where the variation in the degree of

intensity of the main phenomenon (as marked by its principal characters,

Sensation, Thought, Voluntary Motion, &c.) begins to be attended by

conspicuous changes in the miscellaneous properties of the animal. Such

well-marked changes take place, for example, where the class Mammalia

ends; at the points where Fishes are separated from Insects, Insects

from Mollusca, &c. When so formed, the primary natural groups will

compose the series by mere juxtaposition, without redistribution; each

of them corresponding to a definite portion of the scale. In like manner

each family should, if possible, be so subdivided, that one portion of

it shall stand higher and the other lower, though of course contiguous,

in the general scale; and only when this is impossible is it allowable

to ground the remaining subdivisions on characters having no

determinable connexion with the main phenomenon.

Where the principal phenomenon so far transcends in importance all other

properties on which a classification could be grounded, as it does in

the case of animated existence, any considerable deviation from the rule

last laid down is in general sufficiently guarded against by the first

principle of a natural arrangement, that of forming the groups according

to the most important characters. All attempts at a scientific

classification of animals, since first their anatomy and physiology were

successfully studied, have been framed with a certain degree of

instinctive reference to a natural series, and have accorded in many

more points than they have differed, with the classification which would

most naturally have been grounded on such a series. But the accordance

has not always been complete; and it still is often a matter of

discussion, which of several classifications best accords with the true

scale of intensity of the main phenomenon. Cuvier, for example, has been

justly criticized for having formed his natural groups with an undue

degree of reference to the mode of alimentation, a circumstance directly

connected only with organic life, and not lending to the arrangement

most appropriate for the purposes of an investigation of the laws of

animal life, since both carnivorous and herbivorous or frugivorous

animals are found at almost every degree in the scale of animal

perfection. Blainville's classification has been considered by high

authorities to be free from this defect; as representing correctly, by

the mere order of the principal groups, the successive degeneracy of

animal nature from its highest to its most imperfect exemplification.

§ 5. A classification of any large portion of the field of nature in

conformity to the foregoing principles, has hitherto been found

practicable only in one great instance, that of animals. In the case

even of vegetables, the natural arrangement has not been carried beyond

the formation of natural groups. Naturalists have found, and probably

will continue to find it impossible to form those groups into any

series, the terms of which correspond to real gradations in the

phenomenon of vegetative or organic life. Such a difference of degree

may be traced between the class of Vascular Plants and that of Cellular,

which includes lichens, algæ, and other substances whose organization is

simpler and more rudimentary than that of the higher order of

vegetables, and which therefore approach nearer to mere inorganic

nature. But when we rise much above this point, we do not find any

sufficient difference in the degree in which different plants possess

the properties of organization and life. The dicotyledons are of more

complex structure, and somewhat more perfect organization, than the

monocotyledons: and some dicotyledonous families, such as the Compositæ,

are rather more complex in their organization than the rest. But the

differences are not of a marked character, and do not promise to throw

any particular light upon the conditions and laws of vegetable life and

development. If they did, the classification of vegetables would have to

be made, like that of animals, with reference to the scale or series

indicated.

Although the scientific arrangements of organic nature afford as yet the

only complete example of the true principles of rational classification,

whether as to the formation of groups or of series, those principles are

applicable to all cases in which mankind are called upon to bring the

various parts of any extensive subject into mental co-ordination. They

are as much to the point when objects are to be classed for purposes of

art or business, as for those of science. The proper arrangement, for

example, of a code of laws, depends on the same scientific conditions as

the classifications in natural history; nor could there be a better

preparatory discipline for that important function, than the study of

the principles of a natural arrangement, not only in the abstract, but

in their actual application to the class of phenomena for which they

were first elaborated, and which are still the best school for learning

their use. Of this the great authority on codification, Bentham, was

perfectly aware: and his early _Fragment on Government_, the admirable

introduction to a series of writings unequalled in their department,

contains clear and just views (as far as they go) on the meaning of a

natural arrangement, such as could scarcely have occurred to any one who

lived anterior to the age of Linnæus and Bernard de Jussieu.

FOOTNOTES:

[1] Supra, book iii. ch. ii. § 3, 4, 5.

[2] Mr. Bailey has given by far the best statement of this theory. "The

general name," he says, "raises up the image sometimes of one individual

of the class formerly seen, sometimes of another, not unfrequently of

many individuals in succession; and it sometimes suggests an image made

up of elements from several different objects, by a latent process of

which I am not conscious." (Letters on the Philosophy of the Human Mind,

1st series, letter 22.) But Mr. Bailey must allow that we carry on

inductions and ratiocinations respecting the class, by means of this

idea or conception of some one individual in it. This is all I require.

The name of a class calls up some idea, through which we can, to all

intents and purposes, think of the class as such, and not solely of an

individual member of it.

[3] I have entered rather fully into this question in chap. xvii. of _An

Examination of Sir William Hamilton's Philosophy_, headed "The Doctrine

of Concepts or General Notions," which contains my last views on the

subject.

[4] Other examples of inappropriate conceptions are given by Dr. Whewell

(_Phil. Ind. Sc._ ii. 185) as follows:--"Aristotle and his followers

endeavoured in vain to account for the mechanical relation of forces in

the lever, by applying the _inappropriate_ geometrical conceptions of

the properties of the circle: they failed in explaining the _form_ of

the luminous spot made by the sun shining through a hole, because they

applied the _inappropriate_ conception of a circular _quality_ in the

sun's light: they speculated to no purpose about the elementary

composition of bodies, because they assumed the _inappropriate_

conception of _likeness_ between the elements and the compound, instead

of the genuine notion of elements merely _determining_ the qualities of

the compound." But in these cases there is more than an inappropriate

conception; there is a false conception; one which has no prototype in

nature, nothing corresponding to it in facts. This is evident in the

last two examples, and is equally true in the first; the "properties of

the circle" which were referred to, being purely fantastical. There is,

therefore, an error beyond the wrong choice of a principle of

generalization; there is a false assumption of matters of fact. The

attempt is made to resolve certain laws of nature into a more general

law, that law not being one which, though real, is inappropriate, but

one wholly imaginary.

[5] Professor Bain.

[6] This sentence having been erroneously understood as if I had meant

to assert that belief is nothing but an irresistible association, I

think it necessary to observe that I express no theory respecting the

ultimate analysis either of reasoning or of belief, two of the most

obscure points in analytical psychology. I am speaking not of the powers

themselves, but of the previous conditions necessary to enable those

powers to exert themselves: of which conditions I am contending that

language is not one, senses and association being sufficient without it.

[7] Mr. Bailey agrees with me in thinking that whenever "from something

actually present to my senses conjoined with past experience, I feel

satisfied that something has happened, or will happen, or is happening,

beyond the sphere of my personal observation," I may with strict

propriety be said to reason: and of course to reason inductively, for

demonstrative reasoning is excluded by the circumstances of the case.

(_The Theory of Reasoning_, 2nd ed. p. 27.)

[8] _Novum Organum Renovatum_, pp. 35-37.

[9] _Nov. Org. Renov._, pp. 39, 40.

[10] P. 217, 4to edition.

[11] "E, ex, extra, extraneus, étranger, stranger."

Another etymological example sometimes cited is the derivation of the

English _uncle_ from the Latin _avus_. It is scarcely possible for two

words to bear fewer outward marks of relationship, yet there is but one

step between them; _avus_, _avunculus_, _uncle_.

So _pilgrim_, from _ager_: _per agrum_, _peragrinus_, _peregrinus_,

_pellegrino_, _pilgrim_.

[12] P. 226-7.

[13] _Essays_, p. 214.

[14] Ibid. 215.

[15] Such cases give a clear insight into the process of the

degeneration of languages in periods of history when literary culture

was suspended; and we are now in danger of experiencing a similar evil

through the superficial extension of the same culture. So many persons

without anything deserving the name of education have become writers by

profession, that written language may almost be said to be principally

wielded by persons ignorant of the proper use of the instrument, and who

are spoiling it more and more for those who understand it. Vulgarisms,

which creep in nobody knows how, are daily depriving the English

language of valuable modes of expressing thought. To take a present

instance: the verb _transpire_ formerly conveyed very expressively its

correct meaning, viz. to _become known_ through unnoticed channels--to

exhale, as it were, into publicity through invisible pores, like a

vapour or gas disengaging itself. But of late a practice has commenced

of employing this word, for the sake of finery, as a mere synonym of _to

happen_: "the events which have _transpired_ in the Crimea," meaning the

incidents of the war. This vile specimen of bad English is already seen

in the despatches of noblemen and viceroys: and the time is apparently

not far distant when nobody will understand the word if used in its

proper sense. It is a great error to think that these corruptions of

language do no harm. Those who are struggling with the difficulty (and

who know by experience how great it already is) of expressing oneself

clearly with precision, find their resources continually narrowed by

illiterate writers, who seize and twist from its purpose some form of

speech which once served to convey briefly and compactly an unambiguous

meaning. It would hardly be believed how often a writer is compelled to

a circumlocution by the single vulgarism, introduced during the last few

years, of using the word _alone_ as an adverb, _only_ not being fine

enough for the rhetoric of ambitious ignorance. A man will say "to which

I am not alone bound by honour but also by law," unaware that what he

has unintentionally said is, that he is _not alone_ bound, some other

person being bound with him. Formerly if any one said, "I am not alone

responsible for this," he was understood to mean, (what alone his words

mean in correct English,) that he is not the sole person responsible;

but if he now used such an expression, the reader would be confused

between that and two other meanings; that he is not _only responsible_

but something more; or that he is responsible _not only for this_ but

for something besides. The time is coming when Tennyson's [OE]none could

not say "I will not die alone," lest she should be supposed to mean that

she would not only die but do something else.

The blunder of writing _predicate_ for _predict_ has become so widely

diffused that it bids fair to render one of the most useful terms in the

scientific vocabulary of Logic unintelligible. The mathematical and

logical term "to eliminate" is undergoing a similar destruction. All who

are acquainted either with the proper use of the word or with its

etymology, know that to eliminate a thing is to thrust it out; but those

who know nothing about it, except that it is a fine-looking phrase, use

it in a sense precisely the reverse, to denote, not turning anything

out, but bringing it in. They talk of _eliminating_ some truth, or other

useful result, from a mass of details. I suspect that this error must at

first have arisen from some confusion between _to eliminate_ and _to

enucleate_.

Though no such evil consequences as take place in these instances, are

likely to arise from the modern freak of writing _sanatory_ instead of

sanitary, it deserves notice as a charming specimen of pedantry

engrafted upon ignorance. Those who thus undertake to correct the

spelling of the classical English writers, are not aware that the

meaning of _sanatory_, if there were such a word in the language, would

have reference not to the preservation of health, but to the cure of

disease.

[16] _Historical Introduction_, vol. i. pp. 66-8.

[17] _History of Scientific Ideas_, ii. 110, 111.

[18] _Hist. Sc. Id._ ii. 111-113.

[19] _Nov. Org. Renov._ pp. 286, 287.

[20] _Hist. Sc. Id._ ii. 120-122.

[21] I say probably, not certainly, because this is not the

consideration by which a botanist determines what shall or shall not be

admitted as a species. In natural history those objects belong to the

same species, which are, or consistently with experience might have

been, produced from the same stock. But this distinction, in most, and

probably in all cases, happily accords with the other. It seems to be a

law of physiology, that animals and plants do really, in the

philosophical as well as the popular sense, propagate their kind;

transmitting to their descendants all the distinctions of Kind (down to

the most special or lowest Kind) which they themselves possess.

[22] _Nov. Org. Renov._ p. 274.

[23] _Hist. Sc. Id._ i. 133.

[24] Dr. Whewell, in his reply (_Philosophy of Discovery_, p. 270) says

that he "stopped short of, or rather passed by, the doctrine of a series

of organized beings," because he "thought it bad and narrow philosophy."

If he did, it was evidently without understanding this form of the

doctrine; for he proceeds to quote a passage from his "History," in

which the doctrine he condemns is designated as that of "a mere linear

progression in nature, which would place each genus in contact only with

the preceding and succeeding ones." Now the series treated of in the

text agrees with this linear progression in nothing whatever but in

being a progression.

It would surely be possible to arrange all _places_ (for example) in the

order of their distance from the North Pole, though there would be not

merely a plurality, but a whole circle of places at every single

gradation in the scale.

BOOK V.

ON FALLACIES.

"Errare non modo affirmando et negando, sed etiam sentiendo, et in

tacitâ hominum cogitatione contingit."--HOBBES, _Computatio sive

Logica_, ch. v.

"Il leur semble qu'il n'y a qu'à douter par fantaisie, et qu'il n'y a

qu'à dire en général que notre nature est infirme; que notre esprit est

plein d'aveuglement; qu'il faut avoir un grand soin de se défaire de ses

préjugés, et autres choses semblables. Ils pensent que cela suffit pour

ne plus se laisser séduire à ses sens, et pour ne plus se tromper du

tout. Il ne suffit pas de dire que l'esprit est foible, il faut lui

faire sentir ses foiblesses. Ce n'est pas assez de dire qu'il est sujet

à l'erreur, il faut lui découvrir en quoi consistent ses

erreurs."--MALEBRANCHE, _Recherche de la Vérité_.

CHAPTER I.

OF FALLACIES IN GENERAL.

§ 1. It is a maxim of the schoolmen, that "contrariorum eadem est

scientia:" we never really know what a thing is, unless we are also able

to give a sufficient account of its opposite. Conformably to this maxim,

one considerable section, in most treatises on Logic, is devoted to the

subject of Fallacies; and the practice is too well worthy of observance,

to allow of our departing from it. The philosophy of reasoning, to be

complete, ought to comprise the theory of bad as well as of good

reasoning.

We have endeavoured to ascertain the principles by which the sufficiency

of any proof can be tested, and by which the nature and amount of

evidence needful to prove any given conclusion can be determined

beforehand. If these principles were adhered to, then although the

number and value of the truths ascertained would be limited by the

opportunities, or by the industry, ingenuity, and patience, of the

individual inquirer, at least error would not be embraced instead of

truth. But the general consent of mankind, founded on their experience,

vouches for their being far indeed from even this negative kind of

perfection in the employment of their reasoning powers.

In the conduct of life--in the practical business of mankind--wrong

inferences, incorrect interpretations of experience, unless after much

culture of the thinking faculty, are absolutely inevitable: and with

most people, after the highest degree of culture they ever attain, such

erroneous inferences, producing corresponding errors in conduct, are

lamentably frequent. Even in the speculations to which eminent

intellects have systematically devoted themselves, and in reference to

which the collective mind of the scientific world is always at hand to

aid the efforts and correct the aberrations of individuals, it is only

from the more perfect sciences, from those of which the subject-matter

is the least complicated, that opinions not resting on a correct

induction have at length, generally speaking, been expelled. In the

departments of inquiry relating to the more complex phenomena of nature,

and especially those of which the subject is man, whether as a moral and

intellectual, a social, or even as a physical being; the diversity of

opinions still prevalent among instructed persons, and the equal

confidence with which those of the most contrary ways of thinking cling

to their respective tenets, are proof not only that right modes of

philosophizing are not yet generally adopted on those subjects, but that

wrong ones are: that inquirers have not only in general missed the

truth, but have often embraced error; that even the most cultivated

portion of our species have not yet learned to abstain from drawing

conclusions which the evidence does not warrant.

The only complete safeguard against reasoning ill, is the habit of

reasoning well; familiarity with the principles of correct reasoning,

and practice in applying those principles. It is, however, not

unimportant to consider what are the most common modes of bad reasoning;

by what appearances the mind is most likely to be seduced from the

observance of true principles of induction; what, in short, are the most

common and most dangerous varieties of Apparent Evidence, whereby

persons are misled into opinions for which there does not exist evidence

really conclusive.

A catalogue of the varieties of apparent evidence which are not real

evidence, is an enumeration of Fallacies. Without such an enumeration,

therefore, the present work would be wanting in an essential point. And

while writers who included in their theory of reasoning nothing more

than ratiocination, have, in consistency with this limitation, confined

their remarks to the fallacies which have their seat in that portion of

the process of investigation; we, who profess to treat of the whole

process, must add to our directions for performing it rightly, warnings

against performing it wrongly in any of its parts: whether the

ratiocinative or the experimental portion of it be in fault, or the

fault lie in dispensing with ratiocination and induction altogether.

§ 2. In considering the sources of unfounded inference, it is

unnecessary to reckon the errors which arise, not from a wrong method,

nor even from ignorance of the right one, but from a casual lapse,

through hurry or inattention, in the application of the true principles

of induction. Such errors, like the accidental mistakes in casting up a

sum, do not call for philosophical analysis or classification;

theoretical considerations can throw no light upon the means of avoiding

them. In the present treatise our attention is required, not to mere

inexpertness in performing the operation in the right way, (the only

remedies for which are increased attention and more sedulous practice,)

but to the modes of performing it in a way fundamentally wrong; the

conditions under which the human mind persuades itself that it has

sufficient grounds for a conclusion which it has not arrived at by any

of the legitimate methods of induction--which it has not even carelessly

or overhastily, endeavoured to test by those legitimate methods.

§ 3. There is another branch of what may be called the Philosophy of

Error, which must be mentioned here, though only to be excluded from our

subject. The sources of erroneous opinions are twofold, moral and

intellectual. Of these, the moral do not fall within the compass of this

work. They may be classed under two general heads; Indifference to the

attainment of truth, and Bias: of which last the most common case is

that in which we are biassed by our wishes; but the liability is almost

as great to the undue adoption of a conclusion which is disagreeable to

us, as of one which is agreeable, if it be of a nature to bring into

action any of the stronger passions. Persons of timid character are the

more predisposed to believe any statement, the more it is calculated to

alarm them. Indeed it is a psychological law, deducible from the most

general laws of the mental constitution of man, that any strong passion

renders us credulous as to the existence of objects suitable to excite

it.

But the moral causes of opinions, though with most persons the most

powerful of all, are but remote causes: they do not act directly, but by

means of the intellectual causes; to which they bear the same relation

that the circumstances called, in the theory of medicine, _predisposing_

causes, bear to _exciting_ causes. Indifference to truth cannot, in and

by itself, produce erroneous belief; it operates by preventing the mind

from collecting the proper evidences, or from applying to them the test

of a legitimate and rigid induction; by which omission it is exposed

unprotected to the influence of any species of apparent evidence which

offers itself spontaneously, or which is elicited by that smaller

quantity of trouble which the mind may be willing to take. As little is

Bias a direct source of wrong conclusions. We cannot believe a

proposition only by wishing, or only by dreading, to believe it. The

most violent inclination to find a set of propositions true, will not

enable the weakest of mankind to believe them without a vestige of

intellectual grounds--without any, even apparent, evidence. It acts

indirectly, by placing the intellectual grounds of belief in an

incomplete or distorted shape before his eyes. It makes him shrink from

the irksome labour of a rigorous induction, when he has a misgiving that

its result may be disagreeable; and in such examination as he does

institute, it makes him exert that which is in a certain measure

voluntary, his attention, unfairly, giving a larger share of it to the

evidence which seems favourable to the desired conclusion, a smaller to

that which seems unfavourable. It operates, too, by making him look out

eagerly for reasons, or apparent reasons, to support opinions which are

conformable, or resist those which are repugnant, to his interests or

feelings; and when the interests or feelings are common to great numbers

of persons, reasons are accepted and pass current, which would not for a

moment be listened to in that character, if the conclusion had nothing

more powerful than its reasons to speak in its behalf. The natural or

acquired partialities of mankind are continually throwing up

philosophical theories, the sole recommendation of which consists in

the premises they afford for proving cherished doctrines, or justifying

favourite feelings: and when any one of these theories has been so

thoroughly discredited as no longer to serve the purpose, another is

always ready to take its place. This propensity, when exercised in

favour of any widely-spread persuasion or sentiment, is often decorated

with complimentary epithets; and the contrary habit of keeping the

judgment in complete subordination to evidence, is stigmatized by

various hard names, as scepticism, immorality, coldness,

hard-heartedness, and similar expressions according to the nature of the

case. But though the opinions of the generality of mankind, when not

dependent on mere habit and inculcation, have their root much more in

the inclinations than in the intellect, it is a necessary condition to

the triumph of the moral bias that it should first pervert the

understanding. Every erroneous inference, though originating in moral

causes, involves the intellectual operation of admitting insufficient

evidence as sufficient; and whoever was on his guard against all kinds

of inconclusive evidence which can be mistaken for conclusive, would be

in no danger of being led into error even by the strongest bias. There

are minds so strongly fortified on the intellectual side, that they

could not blind themselves to the light of truth, however really

desirous of doing so; they could not, with all the inclination in the

world, pass off upon themselves bad arguments for good ones. If the

sophistry of the intellect could be rendered impossible, that of the

feelings, having no instrument to work with, would be powerless. A

comprehensive classification of all those things which, not being

evidence, are liable to appear such to the understanding, will,

therefore, of itself include all errors of judgment arising from moral

causes, to the exclusion only of errors of practice committed against

better knowledge.

To examine, then, the various kinds of apparent evidence which are not

evidence at all, and of apparently conclusive evidence which do not

really amount to conclusiveness, is the object of that part of our

inquiry into which we are about to enter.

The subject is not beyond the compass of classification and

comprehensive survey. The things, indeed, which are not evidence of any

given conclusion, are manifestly endless, and this negative property,

having no dependence on any positive ones, cannot be made the groundwork

of a real classification. But the things which, not being evidence, are

susceptible of being mistaken for it, are capable of a classification

having reference to the positive property which they possess, of

appearing to be evidence. We may arrange them, at our choice, on either

of two principles; according to the cause which makes them appear to be

evidence, not being so; or according to the particular kind of evidence

which they simulate. The Classification of Fallacies which will be

attempted in the ensuing chapter, is founded on these considerations

jointly.

CHAPTER II.

CLASSIFICATION OF FALLACIES.

§ 1. In attempting to establish certain general distinctions which shall

mark out from one another the various kinds of Fallacious Evidence, we

propose to ourselves an altogether different aim from that of several

eminent thinkers, who have given, under the name of Political or other

Fallacies, a mere enumeration of a certain number of erroneous opinions;

false general propositions which happen to be often met with; _loci

communes_ of bad arguments on some particular subject. Logic is not

concerned with the false opinions which people happen to entertain, but

with the manner in which they come to entertain them. The question is

not, what facts have at any time been erroneously supposed to be proof

of certain other facts, but what property in the facts it was which led

any one to this mistaken supposition.

When a fact is supposed, though incorrectly, to be evidentiary of, or a

mark of, some other fact, there must be a cause of the error; the

supposed evidentiary fact must be connected in some particular manner

with the fact of which it is deemed evidentiary,--must stand in some

particular relation to it, without which relation it would not be

regarded in that light. The relation may either be one resulting from

the simple contemplation of the two facts side by side with one another,

or it may depend on some process of mind, by which a previous

association has been established between them. Some peculiarity of

relation, however, there must be; the fact which can, even by the

wildest aberration, be supposed to prove another fact, must stand in

some special position with regard to it; and if we could ascertain and

define that special position, we should perceive the origin of the

error.

We cannot regard one fact as evidentiary of another, unless we believe

that the two are always, or in the majority of cases, conjoined. If we

believe A to be evidentiary of B, if when we see A we are inclined to

infer B from it, the reason is because we believe that wherever A is, B

also either always or for the most part exists, either as an antecedent,

a consequent, or a concomitant. If when we see A we are inclined not to

expect B--if we believe A to be evidentiary of the absence of B--it is

because we believe that where A is, B either is never, or at least

seldom, found. Erroneous conclusions, in short, no less than correct

conclusions, have an invariable relation to a general formula, either

expressed or tacitly implied. When we infer some fact from some other

fact which does not really prove it, we either have admitted, or, if we

maintained consistency, ought to admit, some groundless general

proposition respecting the conjunction of the two phenomena.

For every property, therefore, in facts, or in our mode of considering

facts, which leads us to believe that they are habitually conjoined when

they are not, or that they are not when in reality they are, there is a

corresponding kind of Fallacy; and an enumeration of fallacies would

consist in a specification of those properties in facts, and those

peculiarities in our mode of considering them, which give rise to this

erroneous opinion.

§ 2. To begin, then; the supposed connexion, or repugnance, between the

two facts, may either be a conclusion from evidence (that is, from some

other proposition or propositions) or may be admitted without any such

ground; admitted, as the phrase is, on its own evidence; embraced as

self-evident, as an axiomatic truth. This gives rise to the first great

distinction, that between Fallacies of Inference, and Fallacies of

Simple Inspection. In the latter division must be included not only all

cases in which a proposition is believed and held for true, literally

without any extrinsic evidence, either of specific experience or general

reasoning; but those more frequent cases in which simple inspection

creates a _presumption_ in favour of a proposition; not sufficient for

belief, but sufficient to cause the strict principles of a regular

induction to be dispensed with, and creating a predisposition to believe

it on evidence which would be seen to be insufficient if no such

presumption existed. This class, comprehending the whole of what may be

termed Natural Prejudices, and which I shall call indiscriminately

Fallacies of Simple Inspection or Fallacies _à priori_, shall be placed

at the head of our list.

Fallacies of Inference, or erroneous conclusions from supposed evidence,

must be subdivided according to the nature of the apparent evidence from

which the conclusions are drawn; or (what is the same thing) according

to the particular kind of sound argument which the fallacy in question

simulates. But there is a distinction to be first drawn, which does not

answer to any of the divisions of sound arguments, but arises out of the

nature of bad ones. We may know exactly what our evidence is, and yet

draw a false conclusion from it; we may conceive precisely what our

premises are, what alleged matters of fact, or general principles, are

the foundation of our inference; and yet, because the premises are

false, or because we have inferred from them what they will not support,

our conclusion may be erroneous. But a case, perhaps even more frequent,

is that in which the error arises from not conceiving our premises with

due clearness, that is, (as shown in the preceding Book,[1]) with due

fixity: forming one conception of our evidence when we collect or

receive it, and another when we make use of it; or unadvisedly, and in

general unconsciously, substituting, as we proceed, different premises

in the place of those with which we set out, or a different conclusion

for that which we undertook to prove. This gives existence to a class of

fallacies which may be justly termed (in a phrase borrowed from Bentham)

Fallacies of Confusion; comprehending, among others, all those which

have their source in language, whether arising from the vagueness or

ambiguity of our terms, or from casual associations with them.

When the fallacy is not one of Confusion, that is, when the proposition

believed, and the evidence on which it is believed, are steadily

apprehended and unambiguously expressed, there remain to be made two

cross divisions. The Apparent Evidence may be either particular facts,

or foregone generalizations; that is, the process may simulate either

simple Induction, or Deduction; and again, the evidence, whether

consisting of supposed facts or of general propositions, may be false in

itself, or, being true, may fail to bear out the conclusion attempted to

be founded on it. This gives us first, Fallacies of Induction and

Fallacies of Deduction, and then a subdivision of each of these,

according as the supposed evidence is false, or true but inconclusive.

Fallacies of Induction, where the facts on which the induction proceeds

are erroneous, may be termed Fallacies of Observation. The term is not

strictly accurate, or rather, not accurately coextensive with the class

of fallacies which I propose to designate by it. Induction is not always

grounded on facts immediately observed, but sometimes on facts inferred:

and when these last are erroneous, the error may not be, in the literal

sense of the term, an instance of bad observation, but of bad inference.

It will be convenient, however, to make only one class of all the

inductions of which the error lies in not sufficiently ascertaining the

facts on which the theory is grounded; whether the cause of failure be

mal-observation, or simple non-observation, and whether the

mal-observation be direct, or by means of intermediate marks which do

not prove what they are supposed to prove. And in the absence of any

comprehensive term to denote the ascertainment, by whatever means, of

the facts on which an induction is grounded, I will venture to retain

for this class of fallacies, under the explanation now given, the title

of Fallacies of Observation.

The other class of inductive fallacies, in which the facts are correct,

but the conclusion not warranted by them, are properly denominated

Fallacies of Generalization: and these, again, fall into various

subordinate classes or natural groups, some of which will be enumerated

in their proper place.

When we now turn to Fallacies of Deduction, namely those modes of

incorrect argumentation in which the premises, or some of them, are

general propositions, and the argument a ratiocination; we may of course

subdivide these also into two species similar to the two preceding,

namely, those which proceed on false premises, and those of which the

premises, though true, do not support the conclusion. But of these

species, the first must necessarily fall under some one of the heads

already enumerated. For the error must be either in those premises which

are general propositions, or in those which assert individual facts. In

the former case it is an Inductive Fallacy, of one or the other class;

in the latter it is a Fallacy of Observation: unless, in either case,

the erroneous premise has been assumed on simple inspection, in which

case the fallacy is _à priori_. Or finally, the premises, of whichever

kind they are, may never have been conceived in so distinct a manner as

to produce any clear consciousness by what means they were arrived at;

as in the case of what is called reasoning in a circle: and then the

fallacy is one of Confusion.

There remain, therefore, as the only class of fallacies having properly

their seat in deduction, those in which the premises of the

ratiocination do not bear out its conclusion; the various cases, in

short, of vicious argumentation, provided against by the rules of the

syllogism. We shall call these, Fallacies of Ratiocination.

We have thus five distinguishable classes of fallacy, which may be

expressed in the following synoptic table:--

Fallacies

of Simple Inspection 1. Fallacies _à priori_.

of Inference

from evidence distinctly

conceived

Inductive Fallacies 2. Fallacies of Observation.

3. Fallacies of Generalization.

Deductive Fallacies 4. Fallacies of Ratiocination.

from evidence indistinctly

conceived 5. Fallacies of Confusion.

§ 3. We must not, however, expect to find that men's actual errors

always, or even commonly, fall so unmistakeably under some one of these

classes, as to be incapable of being referred to any other. Erroneous

arguments do not admit of such a sharply cut division as valid arguments

do. An argument fully stated, with all its steps distinctly set out, in

language not susceptible of misunderstanding, must, if it be erroneous,

be so in some one of these five modes unequivocally: or indeed of the

first four, since the fifth, on such a supposition, would vanish. But it

is not in the nature of bad reasoning to express itself thus

unambiguously. When a sophist, whether he is imposing on himself or

attempting to impose on others, can be constrained to throw his

sophistry into so distinct a form, it needs, in a large proportion of

cases, no further exposure.

In all arguments, everywhere but in the schools, some of the links are

suppressed; _à fortiori_ when the arguer either intends to deceive, or

is a lame and inexpert thinker, little accustomed to bring his reasoning

processes to any test: and it is in those steps of the reasoning which

are made in this tacit and half-conscious, or even wholly unconscious

manner, that the error oftenest lurks. In order to detect the fallacy,

the proposition thus silently assumed must be supplied; but the

reasoner, most likely, has never really asked himself what he was

assuming: his confuter, unless permitted to extort it from him by the

Socratic mode of interrogation, must himself judge what the suppressed

premise ought to be in order to support the conclusion. And hence, in

the words of Archbishop Whately, "it must be often a matter of doubt, or

rather, of arbitrary choice, not only to which genus each _kind_ of

fallacy should be referred, but even to which kind to refer any one

_individual_ fallacy; for since, in any course of argument, _one_

premise is usually suppressed, it frequently happens in the case of a

fallacy, that the hearers are left to the alternative of supplying

_either_ a premise which is _not true_, or _else_, one which _does not

prove_ the conclusion: _e. g._ if a man expatiates on the distress of

the country, and thence argues that the government is tyrannical, we

must suppose him to assume _either_ that 'every distressed country is

under a tyranny,' which is a manifest falsehood, _or_ merely that 'every

country under a tyranny is distressed,' which, however true, proves

nothing, the middle term being undistributed." The former would be

ranked, in our distribution, among fallacies of generalization, the

latter among those of ratiocination. "Which are we to suppose the

speaker meant us to understand? Surely" (if he understood himself) "just

whichever each of his hearers might happen to prefer: some might assent

to the false premise; others allow the unsound syllogism."

Almost all fallacies, therefore, might in strictness be brought under

our fifth class, Fallacies of Confusion. A fallacy can seldom be

absolutely referred to any of the other classes; we can only say, that

if all the links were filled up which should be capable of being

supplied in a valid argument, it would either stand thus (forming a

fallacy of one class), or thus (a fallacy of another); or at furthest we

may say, that the conclusion is most _likely_ to have originated in a

fallacy of such and such a class. Thus in the illustration just quoted,

the error committed may be traced with most probability to a fallacy of

generalization; that of mistaking an uncertain mark, or piece of

evidence, for a certain one; concluding from an effect to some one of

its possible causes, when there are others which would have been equally

capable of producing it.

Yet, though the five classes run into each other, and a particular error

often seems to be arbitrarily assigned to one of them rather than to any

of the rest, there is considerable use in so distinguishing them. We

shall find it convenient to set apart, as Fallacies of Confusion, those

of which confusion is the most obvious characteristic; in which no other

cause can be assigned for the mistake committed, than neglect or

inability to state the question properly, and to apprehend the evidence

with definiteness and precision. In the remaining four classes I shall

place not only the cases in which the evidence is clearly seen to be

what it is, and yet a wrong conclusion drawn from it, but also those in

which, although there be confusion, the confusion is not the sole cause

of the error, but there is some shadow of a ground for it in the nature

of the evidence itself. And in distributing these cases of partial

confusion among the four classes, I shall, when there can be any

hesitation as to the precise seat of the fallacy, suppose it to be in

that part of the process in which, from the nature of the case, and the

tendencies of the human mind, an error would in the particular

circumstances be the most probable.

After these observations we shall proceed, without further preamble, to

consider the five classes in their order.

CHAPTER III.

FALLACIES OF SIMPLE INSPECTION; OR _À PRIORI_ FALLACIES.

§ 1. The tribe of errors of which we are to treat in the first instance,

are those in which no actual inference takes place at all: the

proposition (it cannot in such cases be called a conclusion) being

embraced, not as proved, but as requiring no proof; as a self-evident

truth; or else as having such intrinsic verisimilitude, that external

evidence not in itself amounting to proof, is sufficient in aid of the

antecedent presumption.

An attempt to treat this subject comprehensively would be a

transgression of the bounds prescribed to this work, since it would

necessitate the inquiry which, more than any other, is the grand

question of what is called metaphysics, viz. What are the propositions

which may reasonably be received without proof? That there must be some

such propositions all are agreed, since there cannot be an infinite

series of proof, a chain suspended from nothing. But to determine what

these propositions are, is the _opus magnum_ of the more recondite

mental philosophy. Two principal divisions of opinion on the subject

have divided the schools of philosophy from its first dawn. The one

recognises no ultimate premises but the facts of our subjective

consciousness; our sensations, emotions, intellectual states of mind,

and volitions. These, and whatever by strict rules of induction can be

derived from these, it is possible, according to this theory, for us to

know; of all else we must remain in ignorance. The opposite school hold

that there are other existences, suggested indeed to our minds by these

subjective phenomena, but not inferrible from them, by any process

either of deduction or of induction; which, however, we must, by the

constitution of our mental nature recognise as realities; and

realities, too, of a higher order than the phenomena of our

consciousness, being the efficient causes and necessary substrata of all

Phenomena. Among these entities they reckon Substances, whether matter

or spirit; from the dust under our feet to the soul, and from that to

Deity. All these, according to them, are preternatural or supernatural

beings, having no likeness in experience, though experience is entirely

a manifestation of their agency. Their existence, together with more or

less of the laws to which they conform in their operations, are, on this

theory, apprehended and recognised as real by the mind itself

intuitively: experience (whether in the form of sensation or of mental

feeling) having no other part in the matter than as affording facts

which are consistent with these necessary postulates of reason, and

which are explained and accounted for by them.

As it is foreign to the purpose of the present treatise to decide

between these conflicting theories, we are precluded from inquiring into

the existence, or defining the extent and limits, of knowledge _à

priori_, and from characterizing the kind of correct assumption which

the fallacy of incorrect assumption, now under consideration, simulates.

Yet since it is allowed on both sides that such assumptions are often

made improperly, we may find it practicable, without entering into the

ultimate metaphysical grounds of the discussion, to state some

speculative propositions, and suggest some practical cautions,

respecting the forms in which such unwarranted assumptions are most

likely to be made.

§ 2. In the cases in which, according to the thinkers of the ontological

school, the mind apprehends, by intuition, things, and the laws of

things, not cognizable by our sensitive faculty; those intuitive, or

supposed intuitive, perceptions are undistinguishable from what the

opposite school are accustomed to call ideas of the mind. When they

themselves say that they perceive the things by an immediate act of a

faculty given for that purpose by their Creator, it would be said of

them by their opponents that they find an idea or conception in their

own minds, and from the idea or conception, infer the existence of a

corresponding objective reality. Nor would this be an unfair statement,

but a mere version into other words of the account given by many of

themselves; and one to which the more clear-sighted of them might, and

generally do, without hesitation, subscribe. Since, therefore, in the

cases which lay the strongest claims to be examples of knowledge _à

priori_, the mind proceeds from the idea of a thing to the reality of

the thing itself, we cannot be surprised by finding that illicit

assumptions _à priori_ consist in doing the same thing erroneously: in

mistaking subjective facts for objective, laws of the percipient mind

for laws of the perceived object, properties of the ideas or conceptions

for properties of the things conceived.

Accordingly, a large proportion of the erroneous thinking which exists

in the world proceeds on a tacit assumption, that the same order must

obtain among the objects in nature which obtains among our ideas of

them. That if we always think of two things together, the two things

must always exist together. That if one thing makes us think of another

as preceding or following it, that other must precede it or follow it in

actual fact. And conversely, that when we cannot conceive two things

together they cannot exist together, and that their combination may,

without further evidence, be rejected from the list of possible

occurrences.

Few persons, I am inclined to think, have reflected on the great extent

to which this fallacy has prevailed, and prevails, in the actual beliefs

and actions of mankind. For a first illustration of it, we may refer to

a large class of popular superstitions. If any one will examine in what

circumstances most of those things agree, which in different ages and by

different portions of the human race have been considered as omens or

prognostics of some interesting event, whether calamitous or fortunate;

they will be found very generally characterized by this peculiarity,

that they cause the mind to _think_ of that, of which they are therefore

supposed to forebode the actual occurrence. "Talk of the devil, and he

will appear," has passed into a proverb. Talk of the devil, that is,

raise the idea, and the reality will follow. In times when the

appearance of that personage in a visible form was thought to be no

unfrequent occurrence, it has doubtless often happened to persons of

vivid imagination and susceptible nerves, that talking of the devil has

caused them to fancy they saw him; as, even in our more incredulous

days, listening to ghost stories predisposes us to see ghosts; and thus,

as a prop to the _à priori_ fallacy, there might come to be added an

auxiliary fallacy of mal-observation, with one of false generalization

grounded on it. Fallacies of different orders often herd or cluster

together in this fashion, one smoothing the way for another. But the

origin of the superstition is evidently that which we have assigned. In

like manner it has been universally considered unlucky to speak of

misfortune. The day on which any calamity happened has been considered

an unfortunate day, and there has been a feeling everywhere, and in some

nations a religious obligation, against transacting any important

business on that day. For on such a day our thoughts are likely to be of

misfortune. For a similar reason, any untoward occurrence in commencing

an undertaking has been considered ominous of failure; and often,

doubtless, has really contributed to it, by putting the persons engaged

in the enterprise more or less out of spirits: but the belief has

equally prevailed where the disagreeable circumstance was, independently

of superstition, too insignificant to depress the spirits by any

influence of its own. All know the story of Cæsar's accidentally

stumbling in the act of landing on the African coast; and the presence

of mind with which he converted the direful presage into a favourable

one by exclaiming, "Africa, I embrace thee." Such omens, it is true,

were often conceived as warnings of the future, given by a friendly or a

hostile deity; but this very superstition grew out of a pre-existing

tendency; the god was supposed to send, as an indication of what was to

come, something which people were already disposed to consider in that

light. So in the case of lucky or unlucky names. Herodotus tells us how

the Greeks, on the way to Mycale, were encouraged in their enterprise by

the arrival of a deputation from Samos, one of the members of which was

named Hegesistratus, the leader of armies.

Cases may be pointed out in which something which could have no real

effect but to make persons _think_ of misfortune, was regarded not

merely as a prognostic, but as something approaching to an actual cause

of it. The [Greek: euphêmei] of the Greeks, and _favete linguis_, or

_bona verba quæso_, of the Romans, evince the care with which they

endeavoured to repress the utterance of any word expressive or

suggestive of ill fortune; not from notions of delicate politeness, to

which their general mode of conduct and feeling had very little

reference, but from _bonâ fide_ alarm lest the event so suggested to the

imagination should in fact occur. Some vestige of a similar superstition

has been known to exist among uneducated persons even in our own day: it

is thought an unchristian thing to talk of, or suppose, the death of any

person while he is alive. It is known how careful the Romans were to

avoid, by an indirect mode of speech, the utterance of any word directly

expressive of death or other calamity: how instead of _mortuus est_ they

said _vixit_; and "be the event fortunate or _otherwise_" instead of

_adverse_. The name Maleventum, of which Salmasius so sagaciously

detected the Thessalian origin ([Greek: Maloeis], [Greek: Maloentos]),

they changed into the highly propitious denomination, Beneventum; Egesta

into Segesta; and Epidamnus, a name so interesting in its associations

to the reader of Thucydides, they exchanged for Dyrrhachium, to escape

the perils of a word suggestive of _damnum_ or detriment.

"If an hare cross the highway," says Sir Thomas Browne,[2] "there are

few above threescore that are not perplexed thereat; which

notwithstanding is but an augurial terror, according to that received

expression, _Inauspicatum dat iter oblatus lepus_. And the ground of the

conceit was probably no greater than this, that a fearful animal passing

by us portended unto us something to be feared; as upon the like

consideration the meeting of a fox presaged some future imposture." Such

superstitions as these last must be the result of study; they are too

recondite for natural or spontaneous growth. But when the attempt was

once made to construct a science of predictions, any association, though

ever so faint or remote, by which an object could be connected in

however far-fetched a manner with ideas either of prosperity or of

danger and misfortune, was enough to determine its being classed among

good or evil omens.

An example of rather a different kind from any of these, but falling

under the same principle, is the famous attempt on which so much labour

and ingenuity were expended by the alchemists, to make gold potable. The

motive to this was a conceit that potable gold could be no other than

the universal medicine: and why gold? Because it was so precious. It

must have all marvellous properties as a physical substance, because the

mind was already accustomed to marvel at it.

From a similar feeling, "every substance," says Dr. Paris,[3] "whose

origin is involved in mystery, has at different times been eagerly

applied to the purposes of medicine. Not long since, one of those

showers which are now known to consist of the excrements of insects,

fell in the north of Italy; the inhabitants regarded it as manna, or

some supernatural panacea, and they swallowed it with such avidity, that

it was only by extreme address that a small quantity was obtained for a

chemical examination." The superstition, in this instance, though

doubtless partly of a religious character, probably in part also arose

from the prejudice that a wonderful thing must of course have wonderful

properties.

§ 3. The instances of _à priori_ fallacy which we have hitherto cited

belong to the class of vulgar errors, and do not now, nor in any but a

rude age ever could, impose upon minds of any considerable attainments.

But those to which we are about to proceed, have been, and still are,

all but universally prevalent among thinkers. The same disposition to

give objectivity to a law of the mind--to suppose that what is true of

our ideas of things must be true of the things themselves--exhibits

itself in many of the most accredited modes of philosophical

investigation, both on physical and on metaphysical subjects. In one of

its most undisguised manifestations, it embodies itself in two maxims,

which lay claim to axiomatic truth: Things which we cannot think of

together, cannot coexist; and Things which we cannot help thinking of

together, must coexist. I am not sure that the maxims were ever

expressed in these precise words, but the history both of philosophy and

of popular opinions abounds with exemplifications of both forms of the

doctrine.

To begin with the latter of them: Things which we cannot think of except

together, must exist together. This is assumed in the generally received

and accredited mode of reasoning which concludes that A must accompany B

in point of fact, because "it is involved in the idea." Such thinkers do

not reflect that the idea, being a result of abstraction, ought to

conform to the facts, and cannot make the facts conform to it. The

argument is at most admissible as an appeal to authority; a surmise,

that what is now part of the idea, must, before it became so, have been

found by previous inquirers in the facts. Nevertheless, the philosopher

who more than all others made professions of rejecting authority,

Descartes, constructed his system on this very basis. His favourite

device for arriving at truth, even in regard to outward things, was by

looking into his own mind for it. "Credidi me," says his celebrated

maxim, "pro regulâ generali sumere posse, omne id quod valdè dilucidè et

distinctè concipiebam, verum esse;" whatever can be very clearly

conceived, must certainly exist; that is, as he afterwards explains it,

if the idea includes existence. And on this ground he infers that

geometrical figures really exist, because they can be distinctly

conceived. Whenever existence is "involved in an idea," a thing

conformable to the idea must really exist; which is as much as to say,

whatever the idea contains must have its equivalent in the thing; and

what we are not able to leave out of the idea cannot be absent from the

reality.[4] This assumption pervades the philosophy not only of

Descartes, but of all the thinkers who received their impulse mainly

from him, in particular the two most remarkable among them, Spinoza and

Leibnitz, from whom the modern German metaphysical philosophy is

essentially an emanation. I am indeed disposed to think that the fallacy

now under consideration has been the cause of two-thirds of the bad

philosophy, and especially of the bad metaphysics, which the human mind

has never ceased to produce. Our general ideas contain nothing but what

has been put into them, either by our passive experience, or by our

active habits of thought; and the metaphysicians in all ages, who have

attempted to construct the laws of the universe by reasoning from our

supposed necessities of thought, have always proceeded, and only could

proceed, by laboriously finding in their own minds what they themselves

had formerly put there, and evolving from their ideas of things what

they had first _involved_ in those ideas. In this way all deeply-rooted

opinions and feelings are enabled to create apparent demonstrations of

their truth and reasonableness, as it were out of their own substance.

The other form of the fallacy; Things which we cannot think of together

cannot exist together,--including as one of its branches, that what we

cannot think of as existing cannot exist at all,--may thus be briefly

expressed: Whatever is inconceivable must be false.

Against this prevalent doctrine I have sufficiently argued in a former

Book,[5] and nothing is required in this place but examples. It was

long held that Antipodes were impossible because of the difficulty which

was found in conceiving persons with their heads in the same direction

as our feet. And it was one of the received arguments against the

Copernican system, that we cannot conceive so great a void space as that

system supposes to exist in the celestial regions. When men's

imaginations had always been used to conceive the stars as firmly set in

solid spheres, they naturally found much difficulty in imagining them in

so different, and, as it doubtless appeared to them, so precarious a

situation. But they had no right to mistake the limitation (whether

natural, or, as it in fact proved, only artificial) of their own

faculties, for an inherent limitation of the possible modes of existence

in the universe.

It may be said in objection, that the error in these cases was in the

minor premise, not the major; an error of fact, not of principle; that

it did not consist in supposing that what is inconceivable cannot be

true, but in supposing antipodes to be inconceivable, when present

experience proves that they can be conceived. Even if this objection

were allowed, and the proposition that what is inconceivable cannot be

true were suffered to remain unquestioned as a speculative truth, it

would be a truth on which no practical consequence could ever be

founded, since, on this showing, it is impossible to affirm of any

proposition, not being a contradiction in terms, that it is

inconceivable. Antipodes were really, not fictitiously, inconceivable to

our ancestors: they are indeed conceivable to us; and as the limits of

our power of conception have been so largely extended, by the extension

of our experience and the more varied exercise of our imagination, so

may posterity find many combinations perfectly conceivable to them which

are inconceivable to us. But, as beings of limited experience, we must

always and necessarily have limited conceptive powers; while it does not

by any means follow that the same limitation obtains in the

possibilities of nature, nor even in her actual manifestations.

Rather more than a century and a half ago it was a scientific maxim,

disputed by no one, and which no one deemed to require any proof, that

"a thing cannot act where it is not." With this weapon the Cartesians

waged a formidable war against the theory of gravitation, which,

according to them, involving so obvious an absurdity, must be rejected

_in limine_: the sun could not possibly act upon the earth, not being

there. It was not surprising that the adherents of the old systems of

astronomy should urge this objection against the new; but the false

assumption imposed equally on Newton himself, who in order to turn the

edge of the objection, imagined a subtle ether which filled up the space

between the sun and the earth, and by its intermediate agency was the

proximate cause of the phenomena of gravitation. "It is inconceivable,"

said Newton, in one of his letters to Dr. Bentley,[6] "that inanimate

brute matter should, without the mediation of something else, which is

not material, operate upon and affect other matter _without mutual

contact_.... That gravity should be innate, inherent, and essential to

matter, so that one body may act on another, at a distance, through a

vacuum, without the mediation of anything else, by and through which

their action and force may be conveyed from one to another, is to me so

great an absurdity, that I believe no man, who in philosophical matters

has a competent faculty of thinking, can ever fall into it." This

passage should be hung up in the cabinet of every cultivator of science

who is ever tempted to pronounce a fact impossible because it appears to

him inconceivable. In our own day one would be more tempted, though with

equal injustice, to reverse the concluding observation, and consider the

seeing any absurdity at all in a thing so simple and natural, to be what

really marks the absence of "a competent faculty of thinking." No one

now feels any difficulty in conceiving gravity to be, as much as any

other property is, "inherent, and essential to matter," nor finds the

comprehension of it facilitated in the smallest degree by the

supposition of an ether (though some recent inquirers do give this as an

explanation of it); nor thinks it at all incredible that the celestial

bodies can and do act where they, in actual bodily presence, are not.

To us it is not more wonderful that bodies should act upon one another

"without mutual contact," than that they should do so when in contact;

we are familiar with both these facts, and we find them equally

inexplicable, but equally easy to believe. To Newton, the one, because

his imagination was familiar with it, appeared natural and a matter of

course, while the other, for the contrary reason, seemed too absurd to

be credited.

It is strange that any one, after such a warning, should rely implicitly

on the evidence _à priori_ of such propositions as these, that matter

cannot think; that space, or extension, is infinite; that nothing can be

made out of nothing (_ex nihilo nihil fit_). Whether these propositions

are true or not this is not the place to determine, nor even whether the

questions are soluble by the human faculties. But such doctrines are no

more self-evident truths, than the ancient maxim that a thing cannot act

where it is not, which probably is not now believed by any educated

person in Europe.[7] Matter cannot think; why? because we _cannot

conceive_ thought to be annexed to any arrangement of material

particles. Space is infinite, because having never known any part of it

which had not other parts beyond it, we _cannot conceive_ an absolute

termination. _Ex nihilo nihil fit_, because having never known any

physical product without a pre-existing physical material, we _cannot_,

or think we cannot, _imagine_ a creation out of nothing. But these

things may in themselves be as conceivable as gravitation without an

intervening medium, which Newton thought too great an absurdity for any

person of a competent faculty of philosophical thinking to admit: and

even supposing them not conceivable, this, for aught we know, may be

merely one of the limitations of our very limited minds, and not in

nature at all.

No writer has more directly identified himself with the fallacy now

under consideration, or has embodied it in more distinct terms, than

Leibnitz. In his view, unless a thing was not merely conceivable, but

even explainable, it could not exist in nature. All _natural_ phenomena,

according to him, must be susceptible of being accounted for _à priori_.

The only facts of which no explanation could be given but the will of

God, were miracles properly so called. "Je reconnais," says he,[8]

"qu'il n'est pas permis de nier ce qu'on n'entend pas; mais j'ajoute

qu'on a droit de nier (au moins dans l'ordre naturel) ce qui absolument

n'est point intelligible ni explicable. Je soutiens aussi ... qu'enfin

la conception des créatures n'est pas la mesure du pouvoir de Dieu, mais

que leur conceptivité, ou force de concevoir, est la mesure du pouvoir

de la nature, tout ce qui est conforme à l'ordre naturel pouvant être

conçu ou entendu par quelque créature."

Not content with assuming that nothing can be true which we are unable

to conceive, scientific inquirers have frequently given a still further

extension to the doctrine, and held that, even of things not altogether

inconceivable, that which we can conceive with the greatest ease is

likeliest to be true. It was long an admitted axiom, and is not yet

entirely discredited, that "nature always acts by the simplest means,"

_i.e._ by those which are most easily conceivable.[9] A large proportion

of all the errors ever committed in the investigation of the laws of

nature, have arisen from the assumption that the most familiar

explanation or hypothesis must be the truest. One of the most

instructive facts in scientific history is the pertinacity with which

the human mind clung to the belief that the heavenly bodies must move in

circles, or be carried round by the revolution of spheres; merely

because those were in themselves the simplest suppositions: though, to

make them accord with the facts which were ever contradicting them more

and more, it became necessary to add sphere to sphere and circle to

circle, until the original simplicity was converted into almost

inextricable complication.

§ 4. We pass to another _à priori_ fallacy or natural prejudice, allied

to the former, and originating as that does, in the tendency to presume

an exact correspondence between the laws of the mind and those of things

external to it. The fallacy may be enunciated in this general

form--Whatever can be thought of apart exists apart: and its most

remarkable manifestation consists in the personification of

abstractions. Mankind in all ages have had a strong propensity to

conclude that wherever there is a name, there must be a distinguishable

separate entity corresponding to the name; and every complex idea which

the mind has formed for itself by operating upon its conceptions of

individual things, was considered to have an outward objective reality

answering to it. Fate, Chance, Nature, Time, Space, were real beings,

nay, even gods. If the analysis of qualities in the earlier part of this

work be correct, names of qualities and names of substances stand for

the very same sets of facts or phenomena; _whiteness_ and _a white

thing_ are only different phrases, required by convenience for speaking

of the same external fact under different relations. Not such, however,

was the notion which this verbal distinction suggested of old, either to

the vulgar or to the scientific. Whiteness was an entity, inhering or

sticking in the white substance: and so of all other qualities. So far

was this carried, that even concrete general terms were supposed to be,

not names of indefinite numbers of individual substances, but names of a

peculiar kind of entities termed Universal Substances. Because we can

think and speak of man in general, that is, of all persons in so far as

possessing the common attributes of the species, without fastening our

thoughts permanently on some one individual person; therefore man in

general was supposed to be, not an aggregate of individual persons, but

an abstract or universal man, distinct from these.

It may be imagined what havoc metaphysicians trained in these habits

made with philosophy, when they came to the largest generalizations of

all. _Substantiæ Secundæ_ of any kind were bad enough, but such

Substantiæ Secundæ as [Greek: to on], for example, and [Greek: to hen],

standing for peculiar entities supposed to be inherent in all things

which _exist_, or which are said to be _one_, were enough to put an end

to all intelligible discussion; especially since, with a just perception

that the truths which philosophy pursues are _general_ truths, it was

soon laid down that these general substances were the only subjects of

science, being immutable, while individual substances cognizable by the

senses, being in a perpetual flux, could not be the subject of real

knowledge. This misapprehension of the import of general language

constitutes Mysticism, a word so much oftener written and spoken than

understood. Whether in the Vedas, in the Platonists, or in the

Hegelians, mysticism is neither more nor less than ascribing objective

existence to the subjective creations of our own faculties, to ideas or

feelings of the mind; and believing that by watching and contemplating

these ideas of its own making, it can read in them what takes place in

the world without.

§ 5. Proceeding with the enumeration of _à priori_ fallacies, and

endeavouring to arrange them with as much reference as possible to their

natural affinities, we come to another, which is also nearly allied to

the fallacy preceding the last, standing in the same relation to one

variety of it as the fallacy last mentioned does to the other. This,

too, represents nature as under incapacities corresponding to those of

our intellect; but instead of only asserting that nature cannot do a

thing because we cannot conceive it done, goes the still greater length

of averring that nature does a particular thing, on the sole ground that

we can see no reason why she should not. Absurd as this seems when so

plainly stated, it is a received principle among scientific authorities

for demonstrating _à priori_ the laws of physical phenomena. A

phenomenon must follow a certain law, because we see no reason why it

should deviate from that law in one way rather than in another. This is

called the Principle of the Sufficient Reason;[10] and by means of it

philosophers often flatter themselves that they are able to establish,

without any appeal to experience, the most general truths of

experimental physics.

Take, for example, two of the most elementary of all laws, the law of

inertia and the first law of motion. A body at rest cannot, it is

affirmed, begin to move unless acted upon by some external force:

because, if it did, it must either move up or down, forward or backward,

and so forth; but if no outward force acts upon it, there can be _no

reason_ for its moving up rather than down, or down rather than up, &c.,

_ergo_, it will not move at all.

This reasoning I conceive to be entirely fallacious, as indeed Dr.

Brown, in his treatise on Cause and Effect, has shown with great

acuteness and justness of thought. We have before remarked, that almost

every fallacy may be referred to different genera by different modes of

filling up the suppressed steps; and this particular one may, at our

option, be brought under _petitio principii_. It supposes that nothing

can be a "sufficient reason" for a body's moving in one particular

direction, except some external force. But this is the very thing to be

proved. Why not some _internal_ force? Why not the law of the thing's

own nature? Since these philosophers think it necessary to prove the law

of inertia, they of course do not suppose _it_ to be self-evident; they

must, therefore, be of opinion that, previously to all proof, the

supposition of a body's moving by internal impulse is an admissible

hypothesis; but if so, why is not the hypothesis also admissible, that

the internal impulse acts naturally in some one particular direction,

not in another? If spontaneous motion might have been the law of matter,

why not spontaneous motion towards the sun, towards the earth, or

towards the zenith? Why not, as the ancients supposed, towards a

particular place in the universe, appropriated to each particular kind

of substance? Surely it is not allowable to say that spontaneity of

motion is credible in itself, but not credible if supposed to take place

in any determinate direction.

Indeed, if any one chose to assert that all bodies when uncontrolled set

out in a direct line towards the north pole, he might equally prove his

point by the principle of the Sufficient Reason. By what right is it

assumed that a state of rest is the particular state which cannot be

deviated from without special cause? Why not a state of motion, and of

some particular sort of motion? Why may we not say that the natural

state of a horse left to himself is to amble, because otherwise he must

either trot, gallop, or stand still, and because we know no reason why

he should do one of these rather than another? If this is to be called

an unfair use of the "sufficient reason," and the other a fair one,

there must be a tacit assumption that a state of rest is more natural to

a horse than a state of ambling. If this means that it is the state

which the animal will assume when left to himself, that is the very

point to be proved; and if it does not mean this, it can only mean that

a state of rest is the simplest state, and therefore the most likely to

prevail in nature, which is one of the fallacies or natural prejudices

we have already examined.

So again of the First Law of Motion; that a body once moving will, if

left to itself, continue to move uniformly in a straight line. An

attempt is made to prove this law by saying, that if not, the body must

deviate either to the right or to the left, and that there is no reason

why it should do one more than the other. But who could know,

antecedently to experience, whether there was a reason or not? Might it

not be the nature of bodies, or of some particular bodies, to deviate

towards the right? or if the supposition is preferred, towards the east,

or south? It was long thought that bodies, terrestrial ones at least,

had a natural tendency to deflect downwards; and there is no shadow of

anything objectionable in the supposition, except that it is not true.

The pretended proof of the law of motion is even more manifestly

untenable than that of the law of inertia, for it is flagrantly

inconsistent; it assumes that the continuance of motion in the direction

first taken is more natural than deviation either to the right or to the

left, but denies that one of these can possibly be more natural than the

other. All these fancies of the possibility of knowing what is natural

or not natural by any other means than experience, are, in truth,

entirely futile. The real and only proof of the laws of motion, or of

any other law of the universe, is experience; it is simply that no

other suppositions explain or are consistent with the facts of universal

nature.

Geometers have, in all ages, been open to the imputation of endeavouring

to prove the most general facts of the outward world by sophistical

reasoning, in order to avoid appeals to the senses. Archimedes, says

Professor Playfair,[11] established some of the elementary propositions

of statics by a process in which he "borrows no principle from

experiment, but establishes his conclusion entirely by reasoning _à

priori_. He assumes, indeed, that equal bodies, at the ends of the equal

arms of a lever, will balance one another; and also that a cylinder or

parallelopiped of homogeneous matter, will be balanced about its centre

of magnitude. These, however, are not inferences from experience; they

are, properly speaking, conclusions deduced from the principle of the

Sufficient Reason." And to this day there are few geometers who would

not think it far more scientific to establish these or any other

premises in this way, than to rest their evidence on that familiar

experience which in the case in question might have been so safely

appealed to.