The book includes three works of the great medieval philosopher Thomas Aquinas. In the treatise "On the Unity of Reason Against Averroists," Thomas conducts a polemic with pagan monopsychism and presents his own version of the solution to the psychophysical problem. The treatise "On the Eternity of the World" touches on the philosophical aspects of the question of the emergence of the Universe. The treatise "On Essence and Essence" (presented in a new translation) is devoted to the classical philosophical theme: the relationship of essence and existence. He is accompanied by a fragment from Aristotle's Commentary on Metaphysics, which touches on similar issues.