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.
Thomas AquinasThis Blood that but one drop of has the power to win all the world forgiveness of its world of sin.
Thomas AquinasIf the highest aim of a captain were to preserve his ship, he would keep it in port forever.
Thomas Aquinas