In this passage (the latter part of which especially I can not 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 recognize 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 have been ascertained at the time.

The species of Plants are not only real Kinds, but are probably, 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 sub-classes, 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 recognize 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, etc. 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 any thing 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 can not 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 “can not 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 any thing 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 any thing 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 these 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 can not, 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 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

skillfully and successfully, by the French chemists, though their

nomenclature has become inadequate to the convenient expression of the

very complicated compounds now known to 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 can

not 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 is that which 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 _bursapastoris_, 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_.”(226) 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(227) 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 endeavor 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 any thing 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.(228)

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 connection

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 recognizing 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 recognize 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 recognize 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 toward 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 recognized 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, etc.) 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, etc. 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 connection

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 criticised

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 leading 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 unequaled 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.

Book V.

ON FALLACIES.

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

tacitâ hominum cogitatione contingit.”—HOBBES, _Computatio sive

Logica_, chap. 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 school-men, 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 endeavored 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, endeavored 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 biased 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 can not, 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 can not 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 labor 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

favorable to the desired conclusion, a smaller to that which seems

unfavorable. 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 favorite 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 favor 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 skepticism, 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, can not 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 can not 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 connection, 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 favor 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 _a 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(229)), 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 co-extensive 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

malobservation, or simple non-observation, and whether the malobservation

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 _a 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.

§ 3. We must not, however, expect to find that men’s actual errors always,

or even commonly, fall so unmistakably 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; _a 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 _A 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 can not 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 can not 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 recognizes 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 inferable from them, by

any process either of deduction or of induction; which, however, we must,

by the constitution of our mental nature, recognize 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 recognized 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 _a 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 _a priori_, the mind proceeds from the idea of

a thing to the reality of the thing itself, we can not be surprised by

finding that illicit assumptions _a 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 can not conceive two things together they can not

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 forbode 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 _a

priori_ fallacy, there might come to be added an auxiliary fallacy of

malobservation, 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 favorable 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 εὐφήμει of the Greeks, and _favete linguis_, or _bona verba quæso_, of

the Romans, evince the care with which they endeavored 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 _bona 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 (Μαλόεις, Μαλοέντος), 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 a hare cross the highway,” says Sir Thomas Browne,(230) “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 labor 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 marvelous properties as a physical substance, because the mind was

already accustomed to marvel at it.

From a similar feeling, “every substance,” says Dr. Paris,(231) “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 _a 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 can not think of together, can not

co-exist; and Things which we can not help thinking of together, must

co-exist. 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 can not 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 can not 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 favorite 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 afterward 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 can not be absent from the

reality.(232) 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 can not think of together

can not exist together—including as one of its branches, that what we can

not think of as existing can not 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,(233) 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 can not 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 can not 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 can not 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 can not act where it is not.”(234) 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,(235) “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

any thing 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 _a priori_ of such propositions as these, that matter can

not 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 can not act

where it is not, which probably is not now believed by any educated person

in Europe.(236) Matter can not think; why? because we _can not 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 _can not conceive_ an absolute termination. _Ex nihilo

nihil fit_, because having never known any physical product without a

pre-existing physical material, we _can not_, or think we can not,

_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 _a 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,(237) “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 que 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.(238) 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 _a 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 τὸ ὄν, for example, and τὸ ἔν, standing for peculiar entities

supposed to be inherent in all things which _exist_, or in all 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 _a priori_ fallacies, and

endeavoring 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 can not do a thing

because we can not 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 _a 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;(239) 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 can not, 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, etc., _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 toward the sun,

toward the earth, or toward the zenith? Why not, as the ancients supposed,

toward 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 toward 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 can not 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 toward the right? or

if the supposition is preferred, toward the east, or south? It was long

thought that bodies, terrestrial ones at least, had a natural tendency to

deflect downward; and there is no shadow of any thing 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 endeavoring 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,(240) 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 _a 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.

§ 6. Another natural prejudice, of most extensive prevalence, and which

had a great share in producing the errors fallen into by the ancients in

their physical inquiries, was this: That the differences in nature must

correspond to our received distinctions: that effects which we are

accustomed, in popular language, to call by different names, and arrange

in different classes, must be of different natures, and have different

causes. This prejudice, so evidently of the same origin with those already

treated of, marks more especially the earliest stage of science, when it

has not yet broken loose from the trammels of every-day phraseology. The

extraordinary prevalence of the fallacy among the Greek philosophers may

be accounted for by their generally knowing no other language than their

own; from which it was a consequence that their ideas followed the

accidental or arbitrary combinations of that language, more completely

than can happen among the moderns to any but illiterate persons. They had

great difficulty in distinguishing between things which their language

confounded, or in putting mentally together things which it distinguished;

and could hardly combine the objects in nature, into any classes but those

which were made for them by the popular phrases of their own country; or

at least could not help fancying those classes to be natural and all

others arbitrary and artificial. Accordingly, scientific investigation

among the Greek schools of speculation and their followers in the Middle

Ages, was little more than a mere sifting and analyzing of the notions

attached to common language. They thought that by determining the meaning

of words, they could become acquainted with facts. “They took for

granted,” says Dr. Whewell,(241) “that philosophy must result from the

relations of those notions which are involved in the common use of

language, and they proceeded to seek it by studying such notions.” In his

next chapter, Dr. Whewell has so well illustrated and exemplified this

error, that I shall take the liberty of quoting him at some length.

“The propensity to seek for principles in the common usages of language

may be discerned at a very early period. Thus we have an example of it in

a saying which is reported of Thales, the founder of Greek philosophy.

When he was asked, ‘What is the _greatest_ thing?’ he replied ‘_Place_;

for all other things are _in_ the world, but the world is _in_ it.’ In

Aristotle we have the consummation of this mode of speculation. The usual

point from which he starts in his inquiries is, that _we say_ thus or thus

in common language. Thus, when he has to discuss the question whether

there be, in any part of the universe, a void, or space in which there is

nothing, he inquires first in how many senses we say that one thing is

_in_ another. He enumerates many of these; we say the part is in the

whole, as the finger is _in_ the hand; again we say, the species is in the

genus, as man is included _in_ animal; again, the government of Greece is

_in_ the king; and various other senses are described and exemplified, but

of all these _the most proper_ is when we say a thing is _in_ a vessel,

and generally _in place_. He next examines what _place_ is, and comes to

this conclusion, that ‘if about a body there be another body including it,

it is in place, and if not, not.’ A body moves when it changes its place;

but he adds, that if water be in a vessel, the vessel being at rest, the

parts of the water may still move, for they are included by each other; so

that while the whole does not change its place, the parts may change their

place in a circular order. Proceeding then to the question of a _void_, he

as usual examines the different senses in which the term is used, and

adopts as the most proper, _place without matter_, with no useful result.

“Again, in a question concerning mechanical action, he says, ‘When a man

moves a stone by pushing it with a stick, _we_ say both that the man moves

the stone, and that the stick moves the stone, but the latter _more

properly_.’

“Again, we find the Greek philosophers applying themselves to extract

their dogmas from the most general and abstract notions which they could

detect; for example, from the conception of the Universe as One or as Many

things. They tried to determine how far we may, or must, combine with

these conceptions that of a whole, of parts, of number, of limits, of

place, of beginning or end, of full or void, of rest or motion, of cause

and effect, and the like. The analysis of such conceptions with such a

view, occupies, for instance, almost the whole of Aristotle’s Treatise on

the Heavens.”

The following paragraph merits particular attention: “Another mode of

reasoning, very widely applied in these attempts, was the _doctrine of

contrarieties_, in which it was assumed that adjectives or substances

which are in common language, or in some abstract mode of conception,

opposed to each other, must point at some fundamental antithesis in

nature, which it is important to study. Thus Aristotle says that the

Pythagoreans, from the contrasts which number suggests, collected ten

principles—Limited and Unlimited, Odd and Even, One and Many, Right and

Left, Male and Female, Rest and Motion, Straight and Curved, Light and

Darkness, Good and Evil, Square and Oblong.... Aristotle himself deduced

the doctrine of four elements and other dogmas by oppositions of the same

kind.”

Of the manner in which, from premises obtained in this way, the ancients

attempted to deduce laws of nature, an example is given in the same work a

few pages further on. “Aristotle decides that there is no void on such

arguments as this. In a void there could be no difference of up and down;

for as in nothing there are no differences, so there are none in a

privation or negation; but a void is merely a privation or negation of

matter; therefore, in a void, bodies could not move up and down, which it

is in their nature to do. It is easily seen” (Dr. Whewell very justly

adds) “that such a mode of reasoning elevates the familiar forms of

language, and the intellectual connections of terms, to a supremacy over

facts; making truth depend upon whether terms are or are not privative,

and whether we say that bodies fall _naturally_.”

The propensity to assume that the same relations obtain between objects

themselves, which obtain between our ideas of them, is here seen in the

extreme stage of its development. For the mode of philosophizing,

exemplified in the foregoing instances, assumes no less than that the

proper way of arriving at knowledge of nature, is to study nature itself

subjectively; to apply our observation and analysis not to the facts, but

to the common notions entertained of the facts.

Many other equally striking examples may be given of the tendency to

assume that things which for the convenience of common life are placed in

different classes, must differ in every respect. Of this nature was the

universal and deeply-rooted prejudice of antiquity and the Middle Ages,

that celestial and terrestrial phenomena must be essentially different,

and could in no manner or degree depend on the same laws. Of the same

kind, also, was the prejudice against which Bacon contended, that nothing

produced by nature could be successfully imitated by man: “Calorem solis

et ignis toto genere differre; ne scilicet homines putent se per opera

ignis, aliquid simile iis quæ in Natura fiunt, educere et formare posse;”

and again, “Compositionem tantum opus Hominis, Mistionem vero opus solius

Naturæ esse: ne scilicet homines sperent aliquam ex arte Corporum

naturalium generationem aut transformationem.”(242) The grand distinction

in the ancient scientific speculations, between natural and violent

motions, though not without a plausible foundation in the appearances

themselves, was doubtless greatly recommended to adoption by its

conformity to this prejudice.

§ 7. From the fundamental error of the scientific inquirers of antiquity,

we pass, by a natural association, to a scarcely less fundamental one of

their great rival and successor, Bacon. It has excited the surprise of

philosophers that the detailed system of inductive logic, which this

extraordinary man labored to construct, has been turned to so little

direct use by subsequent inquirers, having neither continued, except in a

few of its generalities, to be recognized as a theory, nor having

conducted in practice to any great scientific results. But this, though

not unfrequently remarked, has scarcely received any plausible

explanation; and some, indeed, have preferred to assert that all rules of

induction are useless, rather than suppose that Bacon’s rules are grounded

on an insufficient analysis of the inductive process. Such, however, will

be seen to be the fact, as soon as it is considered, that Bacon entirely

overlooked Plurality of Causes. All his rules tacitly imply the

assumption, so contrary to all we now know of nature, that a phenomenon

can not have more than one cause.

When he is inquiring into what he terms the forma _calidi aut frigidi,

gravis aut levis, sicci aut humidi_, and the like, he never for an instant

doubts that there is some one thing, some invariable condition or set of

conditions, which is present in all cases of heat, or cold, or whatever

other phenomenon he is considering; the only difficulty being to find what

it is; which accordingly he tries to do by a process of elimination,

rejecting or excluding, by negative instances, whatever is not the _forma_

or cause, in order to arrive at what is. But, that this _forma_ or cause

is _one_ thing, and that it is the same in all hot objects, he has no more

doubt of, than another person has that there is always some cause _or

other_. In the present state of knowledge it could not be necessary, even

if we had not already treated so fully of the question, to point out how

widely this supposition is at variance with the truth. It is particularly

unfortunate for Bacon that, falling into this error, he should have fixed

almost exclusively upon a class of inquiries in which it was especially

fatal; namely, inquiries into the causes of the sensible qualities of

objects. For his assumption, groundless in every case, is false in a

peculiar degree with respect to those sensible qualities. In regard to

scarcely any of them has it been found possible to trace any unity of

cause, any set of conditions invariably accompanying the quality. The

conjunctions of such qualities with one another constitute the variety of

Kinds, in which, as already remarked, it has not been found possible to

trace any law. Bacon was seeking for what did not exist. The phenomenon of

which he sought for the one cause has oftenest no cause at all, and when

it has, depends (as far as hitherto ascertained) on an unassignable

variety of distinct causes.

And on this rock every one must split, who represents to himself as the

first and fundamental problem of science to ascertain what is the cause of

a given effect, rather than what are the effects of a given cause. It was

shown, in an early stage of our inquiry into the nature of Induction,(243)

how much more ample are the resources which science commands for the

latter than for the former inquiry, since it is upon the latter only that

we can throw any direct light by means of experiment; the power of

artificially producing an effect, implying a previous knowledge of at

least one of its causes. If we discover the causes of effects, it is

generally by having previously discovered the effects of causes; the

greatest skill in devising crucial instances for the former purpose may

only end, as Bacon’s physical inquiries did, in no result at all. Was it

that his eagerness to acquire the power of producing for man’s benefit

effects of practical importance to human life, rendering him impatient of

pursuing that end by a circuitous route, made even him, the champion of

experiment, prefer the direct mode, though one of mere observation, to the

indirect, in which alone experiment was possible? Or had even Bacon not

entirely cleared his mind from the notion of the ancients, that “rerum

cognoscere _causas_” was the sole object of philosophy, and that to

inquire into the _effects_ of things belonged to servile and mechanical

arts?

It is worth remarking that, while the only efficient mode of cultivating

speculative science was missed from an undue contempt of manual

operations, the false speculative views thus engendered gave in their turn

a false direction to such practical and mechanical aims as were suffered

to exist. The assumption universal among the ancients and in the Middle

Ages, that there were _principles_ of heat and cold, dryness and moisture,

etc., led directly to a belief in alchemy; in a transmutation of

substances, a change from one Kind into another. Why should it not be

possible to make gold? Each of the characteristic properties of gold has

its _forma_, its essence, its set of conditions, which if we could

discover, and learn how to realize, we could superinduce that particular

property upon any other substance, upon wood, or iron, or lime, or clay.

If, then, we could effect this with respect to every one of the essential

properties of the precious metal, we should have converted the other

substance into gold. Nor did this, if once the premises were granted,

appear to transcend the real powers of mankind. For daily experience

showed that almost every one of the distinctive sensible properties of any

object, its consistence, its color, its taste, its smell, its shape,

admitted of being totally changed by fire, or water, or some other

chemical agent. The _formæ_ of all those qualities seeming, therefore, to

be within human power either to produce or to annihilate, not only did the

transmutation of substances appear abstractedly possible, but the

employment of the power, at our choice, for practical ends, seemed by no

means hopeless.(244)

A prejudice, universal in the ancient world, and from which Bacon was so

far from being free, that it pervaded and vitiated the whole practical

part of his system of logic, may with good reason be ranked high in the

order of Fallacies of which we are now treating.

§ 8. There remains one _a priori_ fallacy or natural prejudice, the most

deeply-rooted, perhaps, of all which we have enumerated; one which not

only reigned supreme in the ancient world, but still possesses almost

undisputed dominion over many of the most cultivated minds; and some of

the most remarkable of the numerous instances by which I shall think it

necessary to exemplify it, will be taken from recent thinkers. This is,

that the conditions of a phenomenon must, or at least probably will,

resemble the phenomenon itself.

Conformably to what we have before remarked to be of frequent occurrence,

this fallacy might without much impropriety have been placed in a

different class, among Fallacies of Generalization; for experience does

afford a certain degree of countenance to the assumption. The cause does,

in very many cases, resemble its effect; like produces like. Many

phenomena have a direct tendency to perpetuate their own existence, or to

give rise to other phenomena similar to themselves. Not to mention forms

actually moulded on one another, as impressions on wax and the like, in

which the closest resemblance between the effect and its cause is the very

law of the phenomenon; all motion tends to continue itself, with its own

velocity, and in its own original direction; and the motion of one body

tends to set others in motion, which is indeed the most common of the

modes in which the motions of bodies originate. We need scarcely refer to

contagion, fermentation, and the like; or to the production of effects by

the growth or expansion of a germ or rudiment resembling on a smaller

scale the completed phenomenon, as in the growth of a plant or animal from

an embryo, that embryo itself deriving its origin from another plant or

animal of the same kind. Again, the thoughts or reminiscences, which are

effects of our past sensations, resemble those sensations; feelings

produce similar feelings by way of sympathy; acts produce similar acts by

involuntary or voluntary imitation. With so many appearances in its favor,

no wonder if a presumption naturally grew up, that causes must

_necessarily_ resemble their effects, and that like could _only_ be

produced by like.

This principle of fallacy has usually presided over the fantastical

attempts to influence the course of nature by conjectural means, the

choice of which was not directed by previous observation and experiment.

The guess almost always fixed upon some means which possessed features of

real or apparent resemblance to the end in view. If a charm was wanted, as

by Ovid’s Medea, to prolong life, all long-lived animals, or what were

esteemed such, were collected and brewed into a broth:

nec defuit illic

Squamea Cinyphii tenuis membrana chelydri

Vivacisque jecur cervi: quibus insuper addit

Ora caputque novem cornicis sæcula passæ.