" Rationality – the ability to grasp forms or essences and to reason on the basis of them – has as its natural end or final cause the attainment of truth, of understanding the world around us. And free will has as its natural end or final cause the choice of those actions that best accord with the truth as it is discovered by reason, and in particular in accord with the truth about a human being’s own nature or essence. That is, as we shall see, exactly what morality is from the point of view of Aristotle and Aquinas: the habitual choice of actions that further the hierarchically ordered natural ends entailed by human nature. "

― Edward Feser , The Last Superstition: A Refutation of the New Atheism