Hold firmly that our faith is identical with that of the ancients. Deny this, and you dissolve the unity of the Church.

If... the motion of the earth were circular, it would be violent and contrary to nature, and could not be eternal, since ... nothing violent is eternal .... It follows, therefore, that the earth is not moved with a circular motion.

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.

Fear is such a powerful emotion for humans that when we allow it to take us over, it drives compassion right out of our hearts.

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.

Art is right reason in the doing of work.

An act of love always tends towards two things; to the good that one wills, and to the person for whom one wills it.