"So thoroughly erroneous is this assertion, that whoever has a proper comprehension of the action of our senses, and understands precisely the nature of that which is transmitted by them to our thinking faculty, will rather affirm that no ideas of things, such as are formed in thought, are brought to us by the senses, so that there is nothing in our ideas which is other than innate in the mind (naturel à l'esprit), or in the faculty of thinking, if only certain circumstances are excepted, which belong only to experience. For example, it is experience alone which causes us to judge that such and such ideas, now present in our minds, are related to certain things which are external to us; not in truth, that they have been sent into our mind by these things, such as they are, by the organs of the senses; but because these organs have transmitted something which has occasioned the mind, in virtue of its innate power, to form them at this time rather than at another....
"Nothing passes from external objects to the soul except certain motions of matter (mouvemens corporels), but neither these motions, nor the figures which they produce, are conceived by us as they exist in the sensory organs, as I have fully explained in my "Dioptrics"; whence it follows that even the ideas of motion and of figures are innate (naturellement en nous). And, à fortiori, the ideas of pain, of colours, of sounds, and of all similar things must be innate, in order that the mind may represent them to itself, on the occasion of certain motions of matter with which they have no resemblance."
Whoever denies what is, in fact, an inconceivable proposition, that sensations pass, as such, from the external world into the mind, must admit the conclusion here laid down by Descartes, that, strictly speaking, sensations, and à fortiori, all the other contents of the mind, are innate. Or, to state the matter in accordance with the views previously expounded, that they are products of the inherent properties of the thinking organ, in which they lie potentially, before they are called into existence by their appropriate causes.
But if all the contents of the mind are innate, what is meant by experience?
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 classes 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 "vérités" or truths: that is beliefs—and his notions respecting them are plainly set forth in a passage 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 (pensée), 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 passages 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' assertion 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 analysis 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 space 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]