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.

The soul is perfected by knowledge and virtue.

The Study of philosophy is not that we may know what men have thought, but what the truth of things is.

The soul is like an uninhabited world that comes to life only when God lays His head against us.

Moral science is better occupied when treating of friendship than of justice.

It would be superfluous to receive by faith, things that can be known by natural reason

Most men seem to live according to sense rather than reason.