If we had to seek paternity for ideas I would much rather turn to Aristotle. It was not without some surprise that I was able to convince myself that the above theory of the relations between the soul and the body is to be found almost in its entirety in the great philosopher. It is true that it is mixed up with many accessory ideas which are out of date and which we now reject; but the essential of the theory is there very clearly formulated, and that is the important point. A few details on this subject will not be out of place. I give them, not from the original source, which I am not erudite enough to consult direct, but from the learned treatise which Bain has published on the psychology of Aristotle, as an appendix to his work on the Senses and the Intelligence.
The whole metaphysics of Aristotle is dominated by the distinction between form and matter. This distinction is borrowed from the most familiar fact in the sensible world—the form of solid objects. We may name a substance without troubling ourselves as to the form it possesses, and we may name the form without regard to the substance that it clothes. But this distinction is a purely abstract one, for there can be no real separation of form from matter, no form without matter, and no matter without form. The two terms are correlative; each one implies the other, and neither can be realised or actualised without the other. Every individual substance can be considered from a triple point of view: 1st, form; 2nd, matter; and 3rd, the compound or aggregate of form and matter, the inseparable Ens, which transports us out of the domain of logic and abstraction into that of reality.
Aristotle recognises between these two logical correlatives a difference in rank. Form is superior, nobler, the higher in dignity, nearer to the perfect entity; matter is inferior, more modest, more distant from perfection. On account of its hierarchical inferiority, matter is often presented as the second, or correlatum, and form as the first, or relatum. This difference in rank is so strongly marked, that these two correlations are likewise conceived in a different form—that of the potential and the actual. Matter is the potential, imperfect, roughly outlined element which is not yet actual, and may perhaps never become so. Form is the actual, the energy, the entelechy which actualises the potential and determines the final compound.
These few definitions will make clear the singularly ingenious idea of Aristotle on the nature of the body, the soul, and of their union. The body is matter which is only intelligible as the correlatum of form; it can neither exist by itself nor be known by itself—that is to say, when considered outside this relation. The soul is form, the actual. By uniting with the body it constitutes the living subject. The soul is the relatum, and is unintelligible and void of sense without its correlatum. "The soul," says Aristotle, "is not a variety of body, but it could not exist without a body: the soul is not a body, but something which belongs or is relative to a body." The animated subject is a form plunged and engaged in matter, and all its actions and passions are so likewise. Each has its formal side which concerns the soul, and its material side which concerns the body. The emotion which belongs to the animated subject or aggregate of soul and body is a complex fact having two aspects logically distinguishable from each other, each of which is correlative to the other and implies it. It is thus not only with our passions, but also with our perceptions, our imaginations, reminiscences, reasonings, and efforts of attention to learn. Intelligence, like emotion, is a phenomenon not simply of the corporeal organism nor of the Νους only, but of the commonalty or association of which they are members, and when the intelligence weakens it is not because the Νους is altered, but because the association is destroyed by the ruin of the corporeal organism.
These few notes, which I have taken in their integrity from Bain's text, allow us thoroughly to comprehend the thought of Aristotle, and it seems to me that the Greek philosopher, by making of the soul and body two correlative terms, has formed a comparison of great exactness. I also much admire his idea according to which it is through the union of the body and soul that the whole, which till then was only possible, goes forth from the domain of logic and becomes actual. The soul actualises the body, and becomes, as he said, its entelechy.
These views are too close to those I have myself just set forth for it to be necessary to dwell on their resemblance. The latter would become still stronger if we separated from the thought of Aristotle a few developments which are not essential, though he allowed them great importance: I refer to the continual comparison he makes with the form and matter of corporeal objects. Happy though it may be, this comparison is but a metaphor which perhaps facilitates the understanding of Aristotle's idea, but is not essential to his theory. For my part, I attach far greater importance to the character of relatum, and correlatum ascribed to the two terms mind and matter, and to the actualisation[42] produced by their union.
Let me add another point of comparison. Aristotle's theory recalls in a striking manner that of Kant on the a priori forms of thought. The form of thought, or the category, is nothing without the matter of cognition, and the latter is nothing without the application of form. "Thoughts without content given by sensation are empty; intuitions without concept furnished by the understanding are blind." There is nothing astonishing in finding here the same illustration, since there is throughout a question of describing the same phenomenon,—the relation of mind to matter.
There remains to us to review the principal types of metaphysical systems. We shall discuss these by taking as our guide the principle we have just evolved, and which may be thus formulated: The phenomena of consciousness constitute an incomplete mode of existence.