One philosopher with detailed recordings of his abstract thoughts and theories is Plato. In the Meno, Socrates' views in the quest for knowledge are challenged with the view that if we know what we are searching for, the search is pointless, and if we do not know what we are searching for, the search is impossible. The second point to this paradox is that learning is a recollection of what the soul lost at birth. Prior to being flesh in the world, the soul knew everything, and when one is born, it loses all of that knowledge. So throughout life, one is to retain what one has forgotten rather than to search for what is unknown.

Plato then claims that if knowledge is recollection, then the soul is immortal. What we recollect is either equality or what equality is. He then forms three different mental states which are...