There would not be a perfect likeness of God in the universe if all things were of one grade of being.

Arrive at knowledge over small streamlets, and do not plunge immediately into the ocean, since progress must go from the easier to the more difficult.

Given the sin of impiety through which they [the Romans] sinned against the divine nature [by idolatry], the punishment that led them to sin against their own nature followed.... I say, therefore, that since they changed into lies [by idolatry] the truth about God, He brought them to ignominious passions, that is, to sins against nature; not that God led them to evil, but only that he abandoned them to evil.

Better to illuminate than merely to shine; to deliver to others contemplated truths than merely to contemplate.

As the saints will rejoice in all goods, so will the damned grieve for all goods.

Man can sin against nature in two ways. First, when he sins against his specific rational nature, acting contrary to reason. In this sense, we can say that every sin is a sin against man's nature, because it is against man's right reason.

In a false person, sacraments do not produce any effect.