My final conclusion, then, about the substantial Soul is that it explains nothing and guarantees nothing. Its successive thoughts are the only intelligible and verifiable things about it, and definitely to ascertain the correlations of these with brain-processes is as much as psychology can empirically do. From the metaphysical point of view, it is true that one may claim that the correlations have a rational ground; and if the word Soul could be taken to mean merely some such vague problematic ground, it would be unobjectionable. But the trouble is that it professes to give the ground in positive terms of a very dubiously credible sort. I therefore feel entirely free to discard the word Soul from the rest of this book. If I ever use it, it will be in the vaguest and most popular way. The reader who finds any comfort in the idea of the Soul, is, however, perfectly free to continue to believe in it; for our reasonings have not established the non-existence of the Soul; they have only proved its superfluity for scientific purposes.
The next theory of the pure Self to which we pass is
The Associationist Theory.
Locke paved the way for it by the hypothesis he suggested of the same substance having two successive consciousnesses, or of the same consciousness being supported by more than one substance. He made his readers feel that the important unity of the Self was its verifiable and felt unity, and that a metaphysical or absolute unity would be insignificant, so long as a consciousness of diversity might be there.
Hume showed how great the consciousness of diversity actually was. In the famous chapter on Personal Identity, in his Treatise on Human Nature, he writes as follows:
"There are some philosophers who imagine we are every moment intimately conscious of what we call our Self; that we feel its existence and its continuance in existence, and are certain, beyond the evidence of a demonstration, both of its perfect identity and simplicity.... Unluckily all these positive assertions are contrary to that very experience which is pleaded for them, nor have we any idea of Self, after the manner it is here explained.... It must be some one impression that gives rise to every real idea.... If any impression gives rise to the idea of Self, that impression must continue invariably the same through the whole course of our lives, since self is supposed to exist after that manner. But there is no impression constant and invariable. Pain and pleasure, grief and joy, passions and sensations succeed each other, and never all exist at the same time.... For my part, when I enter most intimately into what I call myself, I always stumble on some particular perception or other of heat or cold, light or shade, love or hatred, pain or pleasure. I never can catch myself at any time without a perception, and never can observe anything but the perception. When my perceptions are removed for any time, as by sound sleep, so long am I insensible of myself and may truly be said not to exist. And were all my perceptions removed by death, and could I neither think, nor feel, nor see, nor love, nor hate after the dissolution of my body, I should be entirely annihilated, nor do I conceive what is farther requisite to make me a perfect non-entity. If anyone, upon serious and unprejudiced reflection, thinks he has a different notion of himself I must confess I can reason no longer with him. All I can allow him is, that he may be in the right as well as I, and that we are essentially different in this particular. He may, perhaps, perceive something simple and continued which he calls himself; though I am certain there is no such principle in me.
"But setting aside some metaphysicians of this kind, I may venture to affirm of the rest of mankind that they are nothing but a bundle or collection of different perceptions, which succeed each other with an inconceivable rapidity, and are in a perpetual flux and movement. Our eyes cannot turn in their sockets without varying our perceptions. Our thought is still more variable than our sight; and all our other senses and faculties contribute to this change; nor is there any single power of the soul which remains unalterably the same, perhaps for one moment The mind is a kind of theatre, where several perceptions successively make their appearance; pass, repass, glide away and mingle in an infinite variety of postures and situations. There is properly no simplicity in it at one time, nor identity in different; whatever natural propension we may have to imagine that simplicity and identity. The comparison of the theatre must not mislead us. They are the successive perceptions only, that constitute the mind; nor have we the most distant notion of the place where these scenes are represented, nor of the material of which it is composed."
But Hume, after doing this good piece of introspective work, proceeds to pour out the child with the bath, and to fly to as great an extreme as the substantialist philosophers. As they say the Self is nothing but Unity, unity abstract and absolute, so Hume says it is nothing but Diversity, diversity abstract and absolute; whereas in truth it is that mixture of unity and diversity which we ourselves have already found so easy to pick apart. We found among the objects of the stream certain feelings that hardly changed, that stood out warm and vivid in the past just as the present feeling does now; and we found the present feeling to be the centre of accretion to which, de proche en proche, these other feelings are, by the judging Thought, felt to cling. Hume says nothing of the judging Thought; and he denies this thread of resemblance, this core of sameness running through the ingredients of the Self, to exist even as a phenomenal thing. To him there is no tertium quid between pure unity and pure separateness. A succession of ideas "connected by a close relation affords to an accurate view as perfect a notion of diversity as if there was no manner of relation" at all.
"All our distinct perceptions are distinct existences, and the mind never perceives any real connection among distinct existences. Did our perceptions either inhere in something simple or individual, or did the mind perceive some real connection among them, there would be no difficulty in the case. For my part, I must plead the privilege of a sceptic and confess that this difficulty is too hard for my understanding, I pretend not, however, to pronounce it insuperable. Others, perhaps,... may discover some hypothesis that will reconcile these contradictions."[277]
Hume is at bottom as much of a metaphysician as Thomas Aquinas. No wonder he can discover no 'hypothesis.' The unity of the parts of the stream is just as 'real' a connection as their diversity is a real separation; both connection and separation are ways in which the past thoughts appear to the present Thought;—unlike each other in respect of date and certain qualities—this is the separation; alike in other qualities, and continuous in time—this is the connection. In demanding a more 'real' connection than this obvious and verifiable likeness and continuity, Hume seeks 'the world behind the looking glass,' and gives a striking example of that Absolutism which is the great disease of philosophic Thought.