The magnitude of the punishment…

The magnitude of the punishment matches the magnitude of the sin. Now a sin that is against God is infinite; the higher the person against whom it is committed, the graver the sin—it is more criminal to strike a head of state than a private citizen—and God is of infinite greatness. Therefore an infinite punishment is deserved for a sin committed against Him.

Thomas Aquinas, from Summa Theologica, Ia2ae. 87, 4

Sin cannot destroy man’s rationality…

Sin cannot destroy man’s rationality altogether, for then he would no longer be capable of sin.

Thomas Aquinas, quoted in Encyclopedia of Christian Apologetics, by Norman Geisler, under the topic ‘Noetic Effects of Sin’