The author of the article seeks to demonstrate how Aristotle, having put forward in the "Protrepticus" the idea that the person's selfness is essentially identical with the rational "part" of his soul and that it is just in it and thanks to it that the man's "blessedness", "divinity" and "immortality" can be achieved, hereafter substantiates and develops this doctrine in his later works, primarily in the treatises "Metaphysics", "On the Soul" and "Nicomachean Ethics".