In this present life, I reckon that we make the nearest approach to knowledge when we have the least possible concern or interest in the body, and are not saturated with the bodily nature, but remain pure until the hour when God himself is pleased to release us. And then the foolishness of the body will be cleared away and we shall be pure and hold converse with othe pure souls, and know of ourselves the clear light everywhere; and this is surely the light of truth. For no impure thing is allowed to approach the pure. These are the sort of words, Simmias, which the true lovers of wisdom cannot help saying to one another, and thinking.
Plato - Phaedo