which the nature of the soul is described has not much to do with the popular doctrine of the ideas. Yet there is one little trait in the description which shows that they are present to Plato’s mind, namely, the remark that the soul, which had seen truths in the form of the universal (248 C, 249 C), cannot again return to the nature of an animal. [Sidenote: _The conception of them in Meno, Phaedrus, Phaedo,_] In the Phaedo, as in the Meno, the origin of ideas is sought for in a previous state of existence. There was no time when they could have been acquired in this life, and therefore they must have been recovered from another. The process of recovery is no other than the ordinary law of association, by which in daily life the sight of one thing or person recalls another to our minds, and by which in scientific enquiry from any part of knowledge we may be led on to infer the whole. It is also argued that ideas, or rather ideals, must be derived from a previous state of existence because they are more perfect than the sensible forms of them which are given by experience (74 ff.). But in the Phaedo the doctrine of ideas is subordinate to the proof of the immortality of the soul. ‘If the soul existed in a previous state, then it will exist in a future state, for a law of alternation pervades all things.’ And, ‘If the ideas exist, then the soul exists; if not, not.’ It is to be observed, both in the Meno and the Phaedo, that Socrates expresses himself with diffidence. He speaks in the Phaedo (114 D, 115 D) of the words with which he has comforted himself and his friends, and will not be too confident that the description which he has given of the soul and her mansions is exactly true, but he ‘ventures to think that something of the kind is true.’ And in the Meno, after dwelling upon the immortality of the soul, he adds, ‘Of some things which I have said I am not altogether confident’ (cp. 86 C, and Apology, pp. 40 ff.; Gorgias 527 B). From this class of uncertainties he exempts the difference between truth and appearance, of which he is absolutely convinced (98 B). [Sidenote: _in the Republic and Timaeus._]