  Once we properly understand the Phaedo's theory of soul, then, we are in a position to see that it offers a psychological framework that is coherent, though far from fully articulated. But we should also note that the theory is somewhat unsatisfactory, in that it appears rather strikingly to fail to do justice to the unity of the mind. The various activities (etc.) that we characterize as mental or psychological, such as (most importantly) desire and cognition, seem to be, or manifest themselves to us as being, the activities of a single integrated subject; they do not (ordinarily) appear to belong to a plurality of distinct items that operate more or less separately from one another.  When Socrates' contemplation of mathematical truths is disrupted by an intense desire for food, it does not seem to be the case that it is one thing (say, his soul) that has been doing the contemplating and another thing (say, his body) that now wants to get something to eat. It is rather that both contemplation and desire to eat seem to belong to one integrated subject, regardless of whether we wish to say that the subject in question is Socrates' mind, or whether we prefer to say that it is Socrates insofar as he has a mind (or something like that). As things are, the psychological theory of the Phaedo assigns Socrates' contemplation directly to his soul, but leaves his desire for food curiously remote from it, apparently taking ‘bodily’ desire (for instance) to be related to the soul in much the same way in which the operations involved in (say) metabolism and growth are so related. (Those too take place only because his body is ensouled.) It is plausible, though not certain, that Plato felt the force of this problem. It is, in any case, resolved by the new theory of soul that the Republic presents. 