Father Pegues concludes his discussion of the human powers by elaborating upon the intellective faculties of reason and will.
The chief power of knowing in man is his reason, his intellect. Reasoning is an act proper to man because, of all the animals, “man alone is able to reason, or has need of reasoning.” It is a perfection in man to be able to reason. But, it is an imperfection to have need of reasoning, because “he attains to truth by slow degrees only, and he is thereby liable to err.” To know things as they are is to know truth; to not know things as they are is to be either in ignorance or in error. “To be in ignorance is merely not to know things as they are; whereas to be in error is to affirm that a thing is, when it is not, or conversely.” To be in error is an evil, because “man’s proper good consists in knowledge of the truth which is the good of his intellect.”
“Man cannot know God in Himself by the natural force of his reason, for God is infinite above all things I sense. . . . Left then to his natural powers man can know God only imperfectly by his reason.” Nevertheless, “it is a great perfection for man to know God by his reason however imperfect the knowledge be; because thereby man is lifted up in an eminent degree above the rest of creatures that are devoid of reason; it is moreover owing to the possibility of this knowledge that God has raised man to the sovereign dignity of being child of His grace; in this happy state man’s reason knows God as He is in Himself, at first imperfectly by the light of faith, but at length perfectly by the light of glory.”
The soul knows by means of the faculty of reason, and it loves by means of the faculty called the will. The proper object of the intellect is the truth, and the proper object of the will is the good. “His will is not drawn of itself or of necessity to a good except under the general aspect of good; hence provided the good presented to the will is only some particular good the will is master of its own act in so far as it is able to choose or not to choose that particular good. Man’s free will results from a combination of his will with his reason or intellect.”
Quotations from Thomas Pegues, Catechism of the “Summa Theologica” of Saint Thomas Aquinas, trans. Aelred Whitacre (New York: Benziger, 1922).