... if the knowledge which we acquired before birth was lost to us at birth, and afterwords by the use of the senses we recovered that which we previously knew, will not that which we call learning be a process of recovering our knowledge, and may not this be rightly termed recollection by us?... Then, Simmias, our souls must have existed before they were in the form of man—without bodies, and must have had intelligence.

Plato - Phaedo