At this point Cebes recalls Socrates's doctrine of Recollection (ἀνάμνησις) as providing a further proof of the soul's existence before birth. As Simmias has no clear memory of this, Socrates proceeds to expound it fully. The content of our sense-perceptions resembles the Forms, but does so only defectively, and our recognition of this defectiveness implies a pre-natal knowledge of the Forms; thus two ‘equal’ logs are only approximately equal, and remind us of the Form of equality. All so-called learning is really recollection or reminder of this sort. After an argument to rebut the alternative suggestion of innate knowledge, it is emphasised that the doctrine of Forms is interlocked with that of the soul's existence before its incarnation: in other words, they stand or fall together; and Simmias, declaring himself a convinced believer in the Forms, consequently accepts the other doctrine with equal conviction.

To this Cebes rejoined: ‘There is also another theory which, if true, points the same way, Socrates: the one that you are constantly asserting, namely that learning is really just recollection, from which it follows presumably that what we now call to mind we have learnt at some previous time; which would not be possible unless our souls existed somewhere before being born in this human frame. Hence we seem to have another indication that the soul is something immortal.’

Simmias now intervened to ask: ‘But how is that proved, Cebes? Please remind me, as I can't quite remember at the moment.’