St. Thomas Aquinas On Knowledge

“The most perfect beings, such as, for example, intellectual substances, return to their essence with a complete return: knowing something external to themselves, in a certain sense they go outside of themselves; but by knowing that they know, they are already beginning to return to themselves, because the act of cognition mediates between the knower and the thing known.”
— St. Thomas Aquinas, Quaestiones Disputatae de Veritate, 1.9