It is the conversion, by unknown causes, of these innate potentialities into actual existences. The organ of thought, prior to experience, may be compared to an untouched piano, in which it may be properly said that music is innate, inasmuch as its mechanism contains, potentially, so many octaves of musical notes. The unknown cause of sensation which Descartes calls the "je ne sais quoi dans les objets" or "choses telles qu'elles sont," and Kant the "Noumenon" or "Ding an sich," is represented by the musician; who, by touching the keys, converts the potentiality of the mechanism into actual sounds. A note so produced is the equivalent of a single experience.

All the melodies and harmonies that proceed from the piano depend upon the action of the musician upon the keys. There is no internal mechanism which, when certain keys are struck, gives rise to an accompaniment of which the musician is only indirectly the cause. According to Descartes, however--and this is what is generally fixed upon as the essence of his doctrine of innate ideas--the mind possesses such an internal mechanism, by which certain cla.s.ses of thoughts are generated, on the occasion of certain experiences. Such thoughts are innate, just as sensations are innate; they are not copies of sensations, any more than sensations are copies of motions; they are invariably generated in the mind, when certain experiences arise in it, just as sensations are invariably generated when certain bodily motions take place; they are universal, inasmuch as they arise under the same conditions in all men; they are necessary, because their genesis under these conditions is invariable.

These innate thoughts are what Descartes terms "verites" or truths: that is beliefs--and his notions respecting them are plainly set forth in a pa.s.sage of the _Principes_.

"Thus far I have discussed that which we know as things: it remains that I should speak of that which we know as truths. For example, when we think that it is impossible to make anything out of nothing, we do not imagine that this proposition is a thing which exists, or a property of something, but we take it for a certain eternal truth, which has its seat in the mind (_pensee_), and is called a common notion or an axiom. Similarly, when we affirm that it is impossible that one and the same thing should exist and not exist at the same time; that that which has been created should not have been created; that he who thinks must exist while he thinks; and a number of other like propositions; these are only truths, and not things which exist outside our thoughts. And there is such a number of these that it would be wearisome to enumerate them: nor is it necessary to do so, because we cannot fail to know them when the occasion of thinking about them presents itself, and we are not blinded by any prejudices."

It would appear that Locke was not more familiar with Descartes'

writings than Hume seems to have been; for, viewed in relation to the pa.s.sages just cited, the arguments adduced in his famous polemic against innate ideas are totally irrelevant.

It has been shown that Hume practically, if not in so many words, admits the justice of Descartes' a.s.sertion that, strictly speaking, sensations are innate; that is to say, that they are the product of the reaction of the organ of the mind on the stimulus of an "unknown cause,"

which is Descartes' "je ne sais quoi." Therefore, the difference between Descartes' opinion and that of Hume resolves itself into this: Given sensation-experiences, can all the contents of consciousness be derived from the collocation and metamorphosis of these experiences? Or, are new elements of consciousness, products of an innate potentiality distinct from sensibility, added to these? Hume affirms the former position, Descartes the latter. If the a.n.a.lysis of the phenomena of consciousness given in the preceding pages is correct, Hume is in error; while the father of modern philosophy had a truer insight, though he overstated the case. For want of sufficiently searching psychological investigations, Descartes was led to suppose that innumerable ideas, the evolution of which in the course of experience can be demonstrated, were direct or innate products of the thinking faculty.

As has been already pointed out, it is the great merit of Kant that he started afresh on the track indicated by Descartes, and steadily upheld the doctrine of the existence of elements of consciousness, which are neither sense-experiences nor any modifications of them. We may demur to the expression that s.p.a.ce and time are forms of sensory intuition; but it imperfectly represents the great fact that co-existence and succession are mental phenomena not given in the mere sense experience.[23]

FOOTNOTES:

[22] Remarques de Rene Descartes sur un certain placard imprime aux Pays Bas vers la fin de l'annee, 1647.--Descartes, _OEuvres_. Ed. Cousin, x. p. 71.

[23] "Wir konnen uns keinen Gegenstand denken, ohne durch Kategorien; wir konnen keinen gedachten Gegenstand erkennen, ohne durch Anschauungen, die jenen Begriffen entsprechen. Nun sind alle unsere Anschauungen sinnlich, und diese Erkenntniss, so fern der Gegenstand derselben gegeben ist, ist empirisch. Empirische Erkenntniss aber ist Erfahrung. Folglich ist uns keine Erkenntniss _a priori_ moglich, als lediglich von Gegenstanden moglicher Erfahrung."

"Aber diese Erkenntniss, die bloss auf Gegenstande der Erfahrung eingeschrankt ist, ist darum nicht alle von der Erfahrung entlehnt, sondern was sowohl die reinen Anschauungen, als die reinen Verstandesbegriffe betrifft, so sind sie Elemente der Erkenntniss die in uns _a priori_ angetroffen werden."--_Kritik der reinen Vernunft.

Elementarlehre_, p. 135.

Without a glossary explanatory of Kant's terminology, this pa.s.sage would be hardly intelligible in a translation; but it may be paraphrased thus: All knowledge is founded upon experiences of sensation, but it is not all derived from those experiences; inasmuch as the impressions of relation ("reine Anschauungen"; "reine Verstandesbegriffe") have a potential or _a priori_ existence in us, and by their addition to sense-experiences, const.i.tute knowledge.

CHAPTER IV.

THE CLa.s.sIFICATION AND THE NOMENCLATURE OF MENTAL OPERATIONS.

If, as has been set forth in the preceding chapter, all mental states are effects of physical causes, it follows that what are called mental faculties and operations are, properly speaking, cerebral functions, allotted to definite, though not yet precisely a.s.signable, parts of the brain.

These functions appear to be reducible to three groups, namely: Sensation, Correlation, and Ideation.

The organs of the functions of sensation and correlation are those portions of the cerebral substance, the molecular changes of which give rise to impressions of sensation and impressions of relation.

The changes in the nervous matter which bring about the effects which we call its functions, follow upon some kind of stimulus, and rapidly reaching their maximum, as rapidly die away. The effect of the irritation of a nerve-fibre on the cerebral substance with which it is connected may be compared to the pulling of a long bell-wire. The impulse takes a little time to reach the bell; the bell rings and then becomes quiescent, until another pull is given. So, in the brain, every sensation is the ring of a cerebral particle, the effect of a momentary impulse sent along a nerve-fibre.

If there were a complete likeness between the two terms of this very rough and ready comparison, it is obvious that there could be no such thing as memory. A bell records no audible sign of having been rung five minutes ago, and the activity of a sensigenous cerebral particle might similarly leave no trace. Under these circ.u.mstances, again, it would seem that the only impressions of relation which could arise would be those of co-existence and of similarity. For succession implies memory of an antecedent state.[24]

But the special peculiarity of the cerebral apparatus is, that any given function which has once been performed is very easily set a-going again, by causes more or less different from those to which it owed its origin.

Of the mechanism of this generation of images of impressions or ideas (in Hume's sense), which may be termed _Ideation_, we know nothing at present, though the fact and its results are familiar enough.

During our waking, and many of our sleeping, hours, in fact, the function of ideation is in continual, if not continuous, activity.

Trains of thought, as we call them, succeed one another without intermission, even when the starting of new trains by fresh sense-impressions is as far as possible prevented. The rapidity and the intensity of this ideational process are obviously dependent upon physiological conditions. The widest differences in these respects are const.i.tutional in men of different temperaments; and are observable in oneself, under varying conditions of hunger and repletion, fatigue and freshness, calmness and emotional excitement. The influence of diet on dreams; of stimulants upon the fulness and the velocity of the stream of thought; the delirious phantasms generated by disease, by hashish, or by alcohol; will occur to every one as examples of the marvellous sensitiveness of the apparatus of ideation to purely physical influences.

The succession of mental states in ideation is not fortuitous, but follows the law of a.s.sociation, which may be stated thus: that every idea tends to be followed by some other idea which is a.s.sociated with the first, or its impression, by a relation of succession, of contiguity, or of likeness.

Thus the idea of the word horse just now presented itself to my mind, and was followed in quick succession by the ideas of four legs, hoofs, teeth, rider, saddle, racing, cheating; all of which ideas are connected in my experience with the impression, or the idea, of a horse and with one another, by the relations of contiguity and succession. No great attention to what pa.s.ses in the mind is needful to prove that our trains of thought are neither to be arrested, nor even permanently controlled, by our desires or emotions. Nevertheless they are largely influenced by them. In the presence of a strong desire, or emotion, the stream of thought no longer flows on in a straight course, but seems, as it were, to eddy round the idea of that which is the object of the emotion. Every one who has "eaten his bread in sorrow" knows how strangely the current of ideas whirls about the conception of the object of regret or remorse as a centre; every now and then, indeed, breaking away into the new tracks suggested by pa.s.sing a.s.sociations, but still returning to the central thought. Few can have been so happy as to have escaped the social bore, whose pet notion is certain to crop up whatever topic is started; while the fixed idea of the monomaniac is but the extreme form of the same phenomenon.

And as, on the one hand, it is so hard to drive away the thought we would fain be rid of; so, upon the other, the pleasant imaginations which we would so gladly retain are, sooner or later, jostled away by the crowd of claimants for birth into the world of consciousness; which hover as a sort of psychical possibilities, or inverse ghosts, the bodily presentments of spiritual phenomena to be, in the limbo of the brain. In that form of desire which is called "attention," the train of thought, held fast, for a time, in the desired direction, seems ever striving to get on to another line--and the junctions and sidings are so mult.i.tudinous!

The const.i.tuents of trains of ideas may be grouped in various ways.

Hume says:--

"We find, by experience, that when any impression has been present in the mind, it again makes its appearance there as an idea, and this it may do in two different ways: either when, on its new appearance, it retains a considerable degree of its first vivacity, and is somewhat intermediate between an impression and an idea; or when it entirely loses that vivacity, and is a perfect idea. The faculty by which we repeat our impressions in the first manner, is called the _memory_, and the other the _imagination_."--(I. pp. 23, 24.)

And he considers that the only difference between ideas of imagination and those of memory, except the superior vivacity of the latter, lies in the fact that those of memory preserve the original order of the impressions from which they are derived, while the imagination "is free to transpose and change its ideas."

The latter statement of the difference between memory and imagination is less open to cavil than the former, though by no means una.s.sailable.

The special characteristic of a memory surely is not its vividness; but that it is a complex idea, in which the idea of that which is remembered is related by co-existence with other ideas, and by antecedence with present impressions.

If I say I remember A. B., the chance acquaintance of ten years ago, it is not because my idea of A. B. is very vivid--on the contrary, it is extremely faint--but because that idea is a.s.sociated with ideas of impressions co-existent with those which I call A. B.; and that all these are at the end of the long series of ideas, which represent that much past time. In truth I have a much more vivid idea of Mr. Pickwick, or of Colonel Newcome, than I have of A. B.; but, a.s.sociated with the ideas of these persons, I have no idea of their having ever been derived from the world of impressions; and so they are relegated to the world of imagination. On the other hand, the characteristic of an imagination may properly be said to lie not in its intensity, but in the fact that, as Hume puts it, "the arrangement," or the relations, of the ideas are different from those in which the impressions, whence these ideas are derived, occurred; or in other words, that the thing imagined has not happened. In popular usage, however, imagination is frequently employed for simple memory--"In imagination I was back in the old times."

It is a curious omission on Hume's part that, while thus dwelling on two cla.s.ses of ideas, _Memories_ and _Imaginations_, he has not, at the same time, taken notice of a third group, of no small importance, which are as different from imaginations as memories are; though, like the latter, they are often confounded with pure imaginations in general speech.

These are the ideas of expectation, or as they may be called for the sake of brevity, _Expectations_; which differ from simple imaginations in being a.s.sociated with the idea of the existence of corresponding impressions, in the future, just as memories contain the idea of the existence of the corresponding impressions in the past.

The ideas belonging to two of the three groups enumerated: namely, memories and expectations, present some features, of particular interest. And first, with respect to memories.

In Hume's words, all simple ideas are copies of simple impressions. The idea of a single sensation is a faint, but accurate, image of that sensation; the idea of a relation is a reproduction of the feeling of co-existence, of succession, or of similarity. But, when complex impressions or complex ideas are reproduced as memories, it is probable that the copies never give all the details of the originals with perfect accuracy, and it is certain that they rarely do so. No one possesses a memory so good, that if he has only once observed a natural object, a second inspection does not show him something that he has forgotten.

Almost all, if not all, our memories are therefore sketches, rather than portraits, of the originals--the salient features are obvious, while the subordinate characters are obscure or unrepresented.

Now, when several complex impressions which are more or less different from one another--let us say that out of ten impressions in each, six are the same in all, and four are different from all the rest--are successively presented to the mind, it is easy to see what must be the nature of the result. The repet.i.tion of the six similar impressions will strengthen the six corresponding elements of the complex idea, which will therefore acquire greater vividness; while the four differing impressions of each will not only acquire no greater strength than they had at first, but, in accordance with the law of a.s.sociation, they will all tend to appear at once, and will thus neutralise one another.

This mental operation may be rendered comprehensible by considering what takes place in the formation of compound photographs--when the images of the faces of six sitters, for example, are each received on the same photographic plate, for a sixth of the time requisite to take one portrait. The final result is that all those points in which the six faces agree are brought out strongly, while all those in which they differ are left vague; and thus what may be termed a _generic_ portrait of the six, in contradistinction to a _specific_ portrait of any one, is produced.

Thus our ideas of single complex impressions are incomplete in one way, and those of numerous, more or less similar, complex impressions are incomplete in another way; that is to say, they are _generic_, not _specific_. And hence it follows, that our ideas of the impressions in question are not, in the strict sense of the word, copies of those impressions; while, at the same time, they may exist in the mind independently of language.

The generic ideas which are formed from several similar, but not identical, complex experiences are what are commonly called _abstract_ or _general_ ideas; and Berkeley endeavoured to prove that all general ideas are nothing but particular ideas annexed to a certain term, which gives them a more extensive signification, and makes them recall, upon occasion, other individuals which are similar to them. Hume says that he regards this as "one of the greatest and the most valuable discoveries that has been made of late years in the republic of letters," and endeavours to confirm it in such a manner that it shall be "put beyond all doubt and controversy."

I may venture to express a doubt whether he has succeeded in his object; but the subject is an abstruse one; and I must content myself with the remark, that though Berkeley's view appears to be largely applicable to such general ideas as are formed after language has been acquired, and to all the more abstract sort of conceptions, yet that general ideas of sensible objects may nevertheless be produced in the way indicated, and may exist independently of language. In dreams, one sees houses, trees and other objects, which are perfectly recognisable as such, but which remind one of the actual objects as seen "out of the corner of the eye,"

or of the pictures thrown by a badly-focussed magic lantern. A man addresses us who is like a figure seen by twilight; or we travel through countries where every feature of the scenery is vague; the outlines of the hills are ill-marked, and the rivers have no defined banks. They are, in short, generic ideas of many past impressions of men, hills, and rivers. An anatomist who occupies himself intently with the examination of several specimens of some new kind of animal, in course of time acquires so vivid a conception of its form and structure, that the idea may take visible shape and become a sort of waking dream. But the figure which thus presents itself is generic, not specific. It is no copy of any one specimen, but, more or less, a mean of the series; and there seems no reason to doubt that the minds of children before they learn to speak, and of deaf mutes, are peopled with similarly generated generic ideas of sensible objects.

It has been seen that a memory is a complex idea made up of at least two const.i.tuents. In the first place there is the idea of an object; and secondly, there is the idea of the relation of antecedence between that object and some present objects.

To say that one has a recollection of a given event and to express the belief that it happened, are two ways of giving an account of one and the same mental fact. But the former mode of stating the fact of memory is preferable, at present, because it certainly does not presuppose the existence of language in the mind of the rememberer; while it may be said that the latter does. It is perfectly possible to have the idea of an event A, and of the events B, C, D, which came between it and the present state E, as mere mental pictures. It is hardly to be doubted that children have very distinct memories long before they can speak; and we believe that such is the case because they act upon their memories. But, if they act upon their memories, they to all intents and purposes believe their memories. In other words, though, being devoid of language, the child cannot frame a proposition expressive of belief; cannot say "sugar-plum was sweet;" yet the psychical operation of which that proposition is merely the verbal expression, is perfectly effected. The experience of the co-existence of sweetness with sugar has produced a state of mind which bears the same relation to a verbal proposition, as the natural disposition to produce a given idea, a.s.sumed to exist by Descartes as an "innate idea" would bear to that idea put into words.

The fact that the beliefs of memory precede the use of language, and therefore are originally purely instinctive, and independent of any rational justification, should have been of great importance to Hume, from its bearing upon his theory of causation; and it is curious that he has not adverted to it, but always takes the trustworthiness of memories for granted. It may be worth while briefly to make good the omission.

That I was in pain, yesterday, is as certain to me as any matter of fact can be; by no effort of the imagination is it possible for me really to entertain the contrary belief. At the same time, I am bound to admit, that the whole foundation for my belief is the fact, that the idea of pain is indissolubly a.s.sociated in my mind with the idea of that much past time. Any one who will be at the trouble may provide himself with hundreds of examples to the same effect.

This and similar observations are important under another aspect. They prove that the idea of even a single strong impression may be so powerfully a.s.sociated with that of a certain time, as to originate a belief of which the contrary is inconceivable, and which may therefore be properly said to be necessary. A single weak, or moderately strong, impression may not be represented by any memory. But this defect of weak experiences may be compensated by their repet.i.tion; and what Hume means by "custom" or "habit" is simply the repet.i.tion of experiences.