We set forth our petitions before God, not in order to make known to Him our needs and desires, but rather so that we ourselves may realize that in these things it is necessary to turn to God for help.
Thomas AquinasNow it seems that everything in the world stems from sources other than God, since the products of nature have their source in nature; deliberate effects can be traced back to human reason or will as their source. There is no need then to assume that God exists.
Thomas AquinasMan 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 AquinasIt is altogether unlawful to kill oneself... Wherefore suicide is contrary to the inclination of nature, and to charity whereby every man should love himself... Life is God's gift to man, and is subject to His power, Who kills and makes to live. Hence whoever takes his own life, sins against God... for it belongs to God alone to pronounce sentence of death and life.
Thomas Aquinas