Plato and Descrates on the Soul

ABSTRACT Although they are often grouped together in comparison with non-dualist theories, Plato's soul--body dualism, and Descartes' mind--body dualism, are fundamentally different. The doctrines examined are those of the Phaedo and the Meditations. The main difference, from which others flow, lies in Plato's acceptance and Descartes' rejection of the assumption that the soul (= intellect) is identical with what animates the body.

When philosophy teachers present the '-ism's' pertinent to mind-body relations, and are still at the broad-brush stage, quite often one finds them pairing Plato and Descartes as the two most eminent dualists of our Western tradition. As Plato to the through-and-through materialist Democritus, so Descartes to Gassendi, it is often suggested--reasonably, perhaps. As the modern non-reductive materialist to his Cartesian bete noir, so Aristotle to Plato on soul-body relations, we are sometimes told--a misleading analogy, some think. For the purpose of contrast with various non-dualist views it may seem useful to group Plato's dualism and that of Descartes together, and in many contexts their differences may not matter. But if one simply compares the theories with each other, not with any third system, the differences are fascinating and seem important.

Of course there are similarities to sustain the initial pairing. Both philosophers argue that we consist of something incorporeal, whether one calls it 'mind' or 'soul', which for the time being is somehow united with a body that is part of the physical world. Both identify the self, the `I', with the incorporeal member of this alliance. Both hold that my mind or soul will survive the demise of the body by which I am now present to this audience-- which in turn is present to me through its members' bodies. Both may be understood as holding that the mind or soul can exist altogether independently of body, though Plato may have changed position on this point.2 Both are concerned with the immortality of the soul.

Here I shall focus on separability of mind or soul from body in Plato's Phaedo and Descartes' Meditations. But first a word about terms. Several times already I have said 'mind or soul' as if the words meant the same, which of course they do not. Plato consistently speaks of the soul (psuche), but not so Descartes. In his preface addressed to the theologians at the Sorbonne Descartes claims that he will prove the immortality of the soul. He is using the church's label for the doctrine, but it is doubtful that what he thought he could prove is what the church means by the phrase. Roughly, I suppose, the church's meaning spotlights the human individual minus a biological body. It is this that can sin and be forgiven, is summoned to the Last Judgement, has prayers said for its salvation. But what Descartes believed he could show is the immortality of the mind or intellect, and although the mind, as he was for ever stressing, is prone to error and should be expected to conduct itself according to an intellectual code of conduct, its errors are not sins or offences against morality. In more philosophical contexts Descartes explicitly distinguishes mind from soul, reserving 'soul' for that which animates the body. In this sense of 'soul' he either denies that any such principle exists or reduces it to a physical configuration. The biological difference between a living body and a corpse is the purely physical difference between a machine in working order and one that is broken or worn out.

So what Descartes is left with, in addition to his machine-body--if his or any other body even exists, which at the beginning of the Meditations he calls into doubt--is a mind whose business is to think and imagine, but not to animate any corporeal system. And since it is himself that he finds thinking, and since he is unable, no matter how hard he tries, to doubt his own existence as this currently thinking thing, Descartes identifies himself with this mind. But at first he is not in a position to assert that he, or the mind that is he, can exist without the body, because prima facie it is possible that the mind's existence or its essential activity of thinking depends on body in some way. For even though the mind does not require body in the way in which an animating principle presumably requires a body if it is to do its thing of animating something, the mind may depend on the body in some other way, a way in which, so to speak, it is the body that gives life to the mind, much as an arrangement of particles gives rise to a magnetic field. Later on, however, Descartes maintains that according to his clear and distinct ideas of mind and body, neither of these natures contains or refers to the other. And meanwhile he takes himself to have established that everything he clearly and distinctly perceives is true. Hence he can conclude that mind, and perhaps soul in the theological sense, is separable from body, which is the basis for proving the mind or soul immortal.

Or, more precisely, Descartes can conclude that mind and body are separable from each other once he is free of his initial wholesale doubt concerning the real existence of body. For obviously if the physical world is only his finite mind's dream object, neither it nor any of its parts can exist independently of that dreaming. And in that case it may not be easy to show that the finite mind that dreams such a dream--a dream in which it is embodied and its body is part of a physical world--can be free of dreaming this or other dreams like it. But if we take the opposite hypothesis, that the physical world exists independently, then this world, especially the part of it that is Descartes' body, can reasonably be held responsible for the appearances of the physical that are present to Descartes' mind. In that case it is reasonable to assume these appearances will cease when body and mind actually separate. The mind will then be phenomenally unembodied as well as really so. But as long as it is uncertain whether the physical is real independently of the finite mind, one can suppose that either this mind generates the appearances from itself, or they are caused in it by God. But since the finite mind cannot be separated from God any more than it can be separated from itself, on either of these hypotheses the cause of the appearances is necessarily always with that finite mind--so why should it ever be without the appearances? It is true that in the sixth Meditation Descartes says he can clearly and distinctly understand himself to be a complete being even without his faculty of sensory and imaginational appearances. From this he concludes that he or his mind can exist without that faculty and its objects. It follows from this that those objects,