The idea of cause has for centuries been the subject of so many
speculations, that our first care must be to confine ourselves
scrupulously to our subject, i. e., to retrace its evolution simply,
marking the principal phases of its development in the individual and the
species, while as far as possible eliminating whatever lies outside this
one question.
It has been remarked that the word cause signifies sometimes an
antecedent, sometimes a process, sometimes antecedent, process, and
effect produced, taken all three together.[121] This last sense alone is
complete. For, if the primitive, popular conception tends to restrict the
cause to the antecedent, to that which acts, a little reflexion will show
us that the cause is only determined as such by its effect, that the two
terms are correlative, the one not existing without the other. Finally,
with more profound reflexion, the process itself, the transition, the
passage, the _nexus_ between antecedent and consequent, appears as the
vital point, the _proprium quid_ of causality. As psychical fact, as
state of consciousness, therefore, this notion is complex, and among the
elements which compose it, now one and now the other, according to the
epoch, has been considered the most important.
In what follows, we shall have to consider: I. the origin of the idea
of cause in experience; II. its generalisation, and passage from the
individual subjective, to the objective form; III. its transformation as
resulting from the work performed in the various sciences, its scission
into two fundamental ideas: on the one hand, that of force, energy,
active and effective power, cause in the true sense (_vera causa_), which
tends more and more to become a postulate, an x, a metaphysical residuum;
on the other, that of a constant and invariable succession, a fixed
_relation_, which becomes the scientific form of the concept of cause,
equivalent in all respects to the concept of law.
I. Every one seems agreed, fundamentally at least, upon the empirical
origin of the idea of cause. It is of internal, subjective origin;
suggested to us by our motor activity. A being who was hypothetically
perfectly passive, while seeing or feeling constant external sequences,
would have no idea of causality. It would be superfluous to show, by
multiplying our quotations, that spiritualists like Maine de Biran,
empiricists like Mill, critics like Renouvier, all the schools in short,
with varying formulæ, agree upon this point. At the same time it must
not be overlooked that some writers attribute an exclusive privilege
to the “will,” maintaining it to be the type of causality; whereas the
assertion that “our own voluntary action is the exclusive source whence
this idea is derived” is unjustifiable. If, with some authors, the word
“will” is used in a large and vague sense, as designating all mental
activity that is translated by movements, no objection can be raised.
But if it be used in the proper, restricted sense, as meaning a fully
conscious, deliberate act, resulting from motive, the statement cannot
be accepted.[122] Volition is a state that makes its appearance somewhat
tardily. It is preceded by a period of appetites, of needs, instincts,
desires, passions; and all these facts of internal activity, translated
into movements; are as apt as the “will” to engender the empirical
notion of cause, i. e., transitive action, i. e., change produced: they
have moreover the advantage of being anterior in chronological order.
Contemporary psychology has studied the rôle of movements, far more than
any of its predecessors. It attributes to them a capital importance;
it shows that motor elements are included in every intellectual state
without exception, in percepts, in images, and even in concepts. Hence
it feels no repugnance in accepting the common thesis. We must however
remember that the psychology of motion is centred in the consciousness
of muscular effort, which moreover represents the type of primitive
causality. The nature of this sense of effort has given rise to long
and animated debate. For some, it is of central origin: It is anterior
to, or at least concomitant with, the movement produced; it goes from
within outwards—it is efferent. For others, it is of peripheral origin,
posterior to the movement produced; it goes from without, inwards—is
afferent. It is an aggregate of the sensations coming from the
articulations, tendons, muscles, from the rhythm of respiration, etc.:
so that the sense of effort is no more than the consciousness of energy
that _has been_ expended, of movements that _have been_ effectuated: it
is a resultant. This second theory, without so far being decisively and
incontestably established, is daily gaining more adherents, and remains
the most probable. So that, since consciousness of effort is essentially
that of _effect_ produced, it follows that in considering the act as the
source of the idea of cause, we know much less of antecedent than of
consequent. Yet this consciousness of effort produced is not the whole,
whatever people may say, of what is in the primitive conception of a
proper, personal causality. Something more remains: this is the confused
idea, illusory or not, of a _creation_ that proceeds from us. We shall
return to this point.
To conclude: at the outset, the two terms antecedent and consequent, form
almost the exclusive elements in the notion of cause. At any rate, they
preponderate in consciousness, to the exclusion of the third, relation.
The idea of a constant invariable sequence, which was, later on, to be
the intrinsic mark of the causal process, cannot yet be distinguished.
II. The idea of cause—at first strictly individual—soon commences its
movement of extension.
1. During the first period, this extension is the work of the
imagination, rather than of generalisation properly so called. By an
instinctive tendency, well-known, though not explained, man concludes for
intentions, a will, and a causality analogous to his own, in the medium
that acts and reacts around him: his fellows, all living things, and
whatever else by their movements simulate life (clouds, rivers, etc.).
This is the period of primitive fetishism that is fixed in mythologies
and languages. It may actually be observed in children, in savage races,
in brutes (as in the dog that bites the stone by which it is hit),
even in rational man, when—becoming again for the moment a creature of
instinct—he falls into a passion at the table that has hurt him.
This period corresponds fairly well with that of generic images, because
the idea of cause thus generalised results from gross, external, partial,
accidental resemblances, which the mind perceives almost passively.
It cannot be doubted that the higher brutes have a generic image of
causality; i. e., they are capable—given an antecedent—of invariably
representing to themselves the consequence. This mental state, which has
been termed “empirical consecution,” and which is not infrequent even
among men who may never rise beyond it, resolves itself into a permanent
association of ideas, the result of repetition and of habit.[123]
All this, however, is merely an external conception of causality, of
its form, and not its nature; it is an outside view, an approximation.
The proper characteristic of this period is that it remains subjective,
anthropomorphic, representing cause as an intentional activity, which
produces movements only in view of an end.
2. The second period begins with philosophic reflection, and proceeds
by the slow constitution of the sciences. Its development may thus be
summarised: little by little it deprives the notion of cause of its
subjective, human character, without however completely attaining this
ideal end; it reduces the essentials of the concept to a fixed, constant,
and invariable _relation_ between a determined antecedent and consequent;
hence it sees in cause and effect only the two moments, or aspects of
one and the same process, which is fundamentally the affirmation of an
identity.
Here imagination recedes, to make way for abstraction and
generalisation,—for abstraction since it is less a question of terms than
of a certain relation between the terms, for generalisation because
the natural tendency of the mind is to extend causality to the whole of
experience.
It must, however, be remarked that the transition from particular
cases to generalisation, and finally to the universalisation of the
concept of cause, _in a strict sense_, has only been effected little
by little. An opinion that has gained much credit, on the authority of
the _apriorists_, is that every man has an intuitive, innate idea of
the law of causality, as universal. This thesis is equivocal. If it
means that all change suggests to every normal man who witnesses it an
invincible belief in a known or unknown agent of its production, then
the assertion is incontestable: but this, as we have seen, is only the
popular, practical, and external notion of causality. If the true concept
(that of the solidly constituted sciences), which is reducible to an
inflexible, invariable determination, is implied, then it is a fallacy
to pretend that the human mind acquired it at the outset. The belief in
a universal law of causality is no gratuitous gift of nature: it is a
conquest. The fallacy persists, because for at least three centuries this
idea has been propagated by the writings of philosophers and scientists
who have made it familiar enough. None the less, it is a late conception,
unknown to the great mass of the human species. Scientific research began
by establishing laws, (i. e., invariable relations of cause and effect)
between certain groups of phenomena, began by establishing a law of
causality that was valid for these and these only; and the transfer of
this law to all that is known and unknown has only been effected little
by little, and is even yet incomplete. In a word, the law of universal
causality is the generalisation of particular laws, and remains a
postulate.
In support of the above (without entering into historical detail) we may
note the existence in human consciousness of two ideas, which from time
to time, each after its own fashion, give check to the universality of
the principle. Although, from the development of scientific thought,
their influence has been a decreasing factor, they are still very active.
These two ideas are those of miracle and chance.
Miracle, taking this word not in the restricted, religious sense, but
in its etymological acceptance (_mirari_), is a rare and unexpected
event, produced extrinsically to, or against, the ordinary course of
events. The miracle gives no denial to cause, in the popular sense,
because it assumes an antecedent: God, an unknown power. It does deny
it, in the scientific sense, since it is an abrogation of determinism
among phenomena. Miracle is cause without law. Now, for a long period,
no belief could have appeared more natural. In the physical world, the
appearance of a comet, eclipses, and many other things were regarded as
prodigies and warnings. Many races are still imbued with weird fancies
on this subject (monsters that would swallow up the sun or moon, etc.),
and even among civilised men these phenomena produce in many minds a
certain uneasiness. In the biological world, this belief has been much
more tenacious: enlightened spirits in the seventeenth century still
admitted the _errores_ or _lusus naturæ_, held the birth of monstrosities
to be a bad augury, and so on. In the psychological world it has been
even worse. Not to speak of the widely-spread (and not yet extinct)
prejudices of antiquity as to prophetic dreams, auguries of the future;
of the mystery which so long surrounded natural or induced somnambulism,
and analogous contemporary speculations on the occult sciences; of those
who regard liberty as an absolute beginning, etc.: there is, even in
the limited circle of scientific psychology, so little well-determined
relation between cause and effect, that the partisans of contingency may
comfortably imagine anything. Useless to insist upon sociology. We need
only recall the fact that Utopians abound who, while rejecting miracle
in the religious order, admit it freely in the social; believing all
to be possible, and reconstructing human society from top to bottom
according to their dreams. If, finally, we consider that this very dry
and incomplete enumeration covers millions of cases, past and present, we
must recognise that the human mind in its spontaneous and self-governed
progress, experiences no reluctance to admit causes without law.
The idea of chance is more obscure. We might almost say that, for the
majority of people who make no attempt to clear it up, it is an event
that supposes neither cause nor law; it is sheer indetermination, a
cast of the die arriving no one knows how, by means of no one knows
what. It is very evident that chance excludes neither cause nor law,
but evident to those alone who have reflected upon its nature, and
have analysed the notion. To others, it is a mysterious, impenetrable
entity, a _Tyche_ whose acts cannot be foreseen. Hume says that “chance
is only our ignorance of true causes.” Cournot rightly observes that
this is incorrect, that chance involves something real and positive: the
conjunction, the crossing of several sequences of cause and effect, which
are independent of one another by origin, and not naturally intended to
exert any reciprocal influence. Thus one series of causes and effects
lead a traveller to take a particular train: on the other hand a totally
distinct set produces at a given place or time an accident which kills
the man.[124] There is, in short, in chance, no contravention of the laws
of universal mechanism. Why then does it seem to the vulgar mind to be an
exception, indeterminate by nature? First, because the problem set by the
unexpected is insufficiently analysed; but also in my opinion, because
the primitive idea of cause is nearly always that of a single antecedent,
whereas here the unique antecedent is not present, and cannot be
discovered. The conception of a complex causation, constituted by a sum
of concurrent conditions, of equal necessity, is the fruit of advanced
reflexion.
Accordingly, while the man who is formed by scientific discipline refuses
when confronted with these so-called prodigious or fortuitous facts,
to concede that they are exceptions to the law of universal causality,
others are quite ready to admit that the wall that surrounds phenomena
may give way at certain points, with resulting breaches.
From the point of view of pure psychology, it is impossible not to
affirm that the idea of universal causality, of uniformity in the course
of nature, of rigorous determinism (and other analogous formulæ), is
acquired—superposed. Whether this notion be applicable to the whole of
experience, although experience is not yet exhausted, or whether it is
simply a guide to research, a stratagem for introducing order into
things, is a question which psychology has no capacity for discussing,
still less power to resolve.
III. We return to the work of transformation, which, starting with the
notion of cause as it is given in experience—i. e., a force, a power,
that acts and produces—culminates finally in its last term, the law of
causality.
Just as the plurality of objects perceived in nature, forms the
material of the concept of number; as the diverse durations present
in our consciousness are the material of the concept of time; so our
consciousness of acting, of modifying our self and our environment (a
power which we attribute freely to everything that surrounds us) is the
prime material of the concept of cause. But in order that this concept
may be constituted as such—fixed and determined—a work of abstraction
is needed to isolate and bring into relief its distinctive, essential
characteristic from among all the different elements that compose the
primitive and complex notion of empirical cause (antecedent, consequent,
action or reaction, change, transformation, etc.). This distinctive
characteristic is an invariable relation of sequence (the conditions
being supposed the same); and the establishment of it has been, almost
exclusively, the result of scientific research.
A history of the secular fluctuations in the idea of cause, as affected
by the various philosophical theories and changes of method in the
sciences, would be the best review of the phases of its evolution.
Impossible here to attempt such a task. We may only note the two extreme
points: the speculations of antiquity, and the contemporaneous aspect of
the question.[125]
The ancient philosophers who (at least during the great eras) were at
once metaphysicians and scientists, constructed systems of cosmogony and
assumed “first causes,” which were conceived either as forces, principles
of action, motive elements of nature (water, air, fire, atoms), or
as rational types (numbers, ideas). On the other hand they invented
mathematics, and laid the foundations of astronomy and physics. Now, as
regards causality, these essays at the scientific investigation of nature
involved consequences which were not plainly disclosed until a much
later period. They exacted another position,—a passage from subjective
to objective: whether in relation to the fall of bodies, or to a law
of hydrostatics (such as that to which Archimedes gave his name), any
one who studies the physical world necessarily sees its changes from
without. He considers cause no longer as an internal factor revealed
by consciousness, but as a sequence given by the senses. Antecedents,
consequents, invariable succession, are for him the only useful data.
Conditions equal cause; and the important determination is that not of an
operating entity, but of a constant relation. This—the only scientific
conception of cause—it is which is covered by Stuart Mill’s definition:
“Cause is the sum of the positive and negative conditions, which, when
given, are followed by an invariable consequent.”
This external aspect, old as science itself, was big with consequences
that have only been clearly revealed in our own day, and which may
be summed up in a word as identity of cause and effect. There is no
separation between the two; the antecedent is not one thing and the
consequent another; they are two manifestations, different in time, of
a fundamental unity. It has rightly been observed that the mechanical
theory of the universe (correlation of forces, conservation and
transformation of energy, etc.) is the contemporaneous form of the
concept of natural causality. Expressed from earliest antiquity in the
form of a metaphysical anticipation (_ex nihilo nihil_), it enters in the
seventeenth century upon its scientific phase, and is completed in our
own day. The physicists who have established it upon experience and by
calculation, saw plainly the consequences it involved. To cite only one
instance, R. Mayer in his _Mechanik der Wärme_ says, “If the cause _c_
produces the effect _e_, then _c_ = _e_; if _e_ is the cause of another
effect _f_, then _e_ = _f_, and so on. Since _c_ becomes _e_, _e_ = _f_,
etc., we must consider these magnitudes as the different phenomenal
forms of one and the same object. Just as the first property of cause
is its indestructibility, so the second property is convertibility,
i. e., capacity for assuming different forms. And this capacity must
not be regarded as a metamorphosis; each cause is invariable, but
the combination of its relations is variable. There is quantitative
indestructibility and qualitative convertibility.”
It must not be forgotten that the general principles of
thermodynamics—the latest form of the concept of natural causality—are
not absolute, but are proposed as ideal. We know, _e. g._, that heat can
never give rise again to all the work from which it was produced, that
no physical event is exactly reversible, _i. e._ it cannot be reproduced
identically at the opposite end of the process, because in its first
appearance it had to overcome resistance, and thus lost part of its
energy. All this, however, is outside our scope. As much as the doctrine
of the conservation of energy is valid, so much is the actual concept of
natural causality worth. We merely undertook to follow the evolution of
this concept down to the present day, to point out its transformations,
without in any way prejudging the future, or still less attributing to it
any absolute value.[126]
What now becomes of the idea of causality taken in the other sense,
no longer as an invariable relation of antecedent to consequent,
but as a thing that acts, creates, modifies, or persists under all
transformations and clothes all masks? The scientific method, as soon
as it penetrates into any order of phenomena, tends to exclude cause, to
reduce it to the strictest limits, to make the least possible use of it.
Cause then becomes the synonym of force. But physical science defines
force only by its effects:—movement, or work done. So, too, the biologist
rejects the notion of “vital force”; non-metaphysical psychology will
have none of the “faculties,” intervention of “the soul,” and the like.
Is the notion thus discarded, totally suppressed? Nay,—for even in
mechanics and physics it cannot be entirely eliminated. It is there as a
postulate, a residuum, an unknown factor covering lacunæ. Yet, do what
we will, force or energy, in order to be more than an empty word and to
become intelligible, can only be represented and imagined under the form
of the muscular effort whence it originates, and which is its type; and
despite all the elaborations to which it is submitted in order to rid it
of its anthropomorphical character, and dehumanise it, it remains rather
a fact of internal experience than a concept. Is it destined to undergo
other transformations, by reason of more profound apprehension, or some
new aspect of the problem? Is there—along with mechanical causality and
rigorous determinism—room for any other mode of causality, proper to
psychology, to linguistics, to history, in short to the positive sciences
of the mind, as is maintained by Wundt and others? The secret remains for
the future.
The natural tendency of the mind (which is but one aspect of the instinct
of conservation) to seek and investigate in face of the unknown and
unexpected, its clear or confused need of explanation for better or
worse, at the outset concluded for an acting entity. The idea still
survives under a naïve or transcendental form; it reappears in every
unexplained contingency, whether in regard to the first origin of things,
or (for the partisans of liberty) to freedom of action. In this sense,
“causality is an altar to the Unknown God, an empty pedestal that awaits
its statue.”[127]
In its other sense, which is widely different and even contrary,
which has been slowly fixed, and more slowly extended to the whole of
experience, cause is a true concept: the resultant namely of abstraction,
summarised in the characters exclusively proper to it. Under this form it
is equivalent to the concept of law.