Thomas Aquinas

“ Because, in speculative matters, it is impossible to convince one who errs in the principles, whereas one who errs, but retains the principles, can be brought back to the truth by means of the principles. Likewise in practical matters, he who, by sinning, turns away from his last end, if we consider the nature of his sin, falls irreparably, and therefore is said to sin mortally and to deserve eternal punishment: whereas when a man sins without turning away from God, by the very nature of his sin, his disorder can be repaired, because the principle of the order is not destroyed ”

“ For whatever things are comprised under the order of reason, are comprised under the order of God Himself. Yet some things are comprised under the order of God, which surpass the human reason, such as matters of faith, and things due to God alone. Hence he that sins in such matters, for instance, by heresy, sacrilege, or blasphemy, is said to sin against God. ”

“ It is not the sinner's intention to depart from reason; and so sins of excess and deficiency do not become of one kind through departing from the one rectitude of reason. On the other hand, sometimes he who utters a falsehood, intends to hide the truth, wherefore in this respect, it matters not whether he tells more or less. If, however, departure from the truth be not outside the intention, it is evident that then one is moved by different causes to tell more or less ”

“ Now there should be a threefold order in man: one in relation to the rule of reason, in so far as all our actions and passions should be commensurate with the rule of reason: another order is in relation to the rule of the Divine Law, whereby man should be directed in all things: and if man were by nature a solitary animal, this twofold order would suffice. But since man is naturally a civic and social animal, as is proved in Polit. i, 2, hence a third order is necessary, whereby man is directed in relation to other men among whom he has to dwell. ”

“ To sin against God is common to all sins, in so far as the order to God includes every human order; but in so far as order to God surpasses the other two orders, sin against God is a special kind of sin. ”

“ Yet in some things we are directed according to reason, in relation to ourselves only, and not in reference to our neighbor; and when man sins in these matters, he is said to sin against himself, as is seen in the glutton, the lustful, and the prodigal. ”

“ When several things, of which one includes another, are distinct from one another, this distinction is understood to refer, not to the part contained in another, but to that in which one goes beyond another. ”

“ For even as in the body, the disorder of death which results from the destruction of the principle of life, is irreparable according to nature, while the disorder of sickness can be repaired by reason of the vital principle being preserved, so it is in matters concerning the soul. ”

“ In God's law, the necessity for various affirmative and negative precepts, was that men might be gradually led to virtue, first by abstaining from evil, being induced to this by the negative precepts, and afterwards by doing good, to which we are induced by the affirmative precepts. Wherefore the affirmative and negative precepts do not belong to different virtues, but to different degrees of virtue; and consequently they are not of necessity, opposed to sins of different species. ”

“ Accordingly, if we refer to the material species in sins of omission and commission, they differ specifically, using species in a broad sense, in so far as negation and privation may have a species. But if we refer to the formal species of sins of omission and commission, they do not differ specifically, because they are directed to the same end, and proceed from the same motive. For the covetous man, in order to hoard money, both robs, and omits to give what he ought, and in like manner, the glutton, to satiate his appetite, both eats too much and omits the prescribed fasts. ”

“ Further, every division should consist of things in opposition to one another. But these three kinds of sin are not opposed to one another: for whoever sins against his neighbor, sins against himself and against God. ”

“ We must therefore say that the difference between venial and mortal sin, or any other difference is respect of the debt of punishment, cannot be a difference constituting specific diversity. For what is accidental never constitutes a species ”

“ Further, evil, being a privation, differs specifically according to the different species of opposites. Now sin is an evil in the genus of human acts. Therefore sins differ specifically according to their opposites rather than according to their objects. ”

“ On the other hand, the active principles in voluntary acts, such as the acts of sins, are not determined, of necessity, to one act, and consequently from one active or motive principle, diverse species of sins can proceed: thus from fear engendering false humility man may proceed to theft, or murder, or to neglect the flock committed to his care ”

“ Therefore when the soul is so disordered by sin as to turn away from its last end, viz. God, to Whom it is united by charity, there is mortal sin; but when it is disordered without turning away from God, there is venial sin. ”

“ Sometimes, however, the corruption of different circumstances arises from different motives: for instance that a man eat hastily, may be due to the fact that he cannot brook the delay in taking food, on account of a rapid exhaustion of the digestive humors ”

“ In like manner, the first order includes the third and surpasses it, because in all things wherein we are directed in reference to our neighbor, we need to be directed according to the order of reason. ”