There Ain't No Such Thing as Philosophical-Only Sin

DURING THE GREAT DEBATE between the casuistic Jesuit theologians (who were prone to laxity) and the Jansenists (who were prone to rigorism), a concept known as philosophical sin (peccatum philosophicum) developed. The theory was that for an act to be formally sinful (as distinguished from materially, or objectively sinful), there had to be advertence to the act as sinful and knowledge that the act was a violation of a precept of God. If both components did not exist, then the sin was not theological (peccatum theologicum), but was only philosophical (peccatum philosophicum). Whereas theological sin was a sin against both God and reason, philosophical sin was an offense only against reason, since the actor (be he an atheist, or simply ignorant that an act, say use of artificial contraception, was against the law of God). One had to had knowledge of God as legislator to be guilty of theological sin. Some, however, rejected this distinction as artificial, and, like the Spanish Cistercian Juan Caramuel y Lobkowitz (1606-1682), whom St. Alphonsus Liguori called the "Prince of the Laxists," found a middle road, arguing that while a person may not have knowledge of an act being against God as legislator, he would have knowledge, even if implicit, of the offense against God as creator.*

The notion of distinguishing between philosophical and theological sin appears to have been first proposed by a Jesuit named Dereux (who was president of a Jesuit college in Dijon, France) and defended by Etienne Bougot. According to this concept (the Dijon thesis):

Peccatum Philosophicum, or moral sin, is a human act incompatible with rational nature and right reason. Peccatum Theologicum, or moral sin, is free transgression of divine law. The Philosophicum, however grave, in a man who is ignorant of God, or who in the act does not think of God, is a grave sin, but is not an offence to God, nor a moral sin sundering friendship with God, nor worthy of eternal punishments.

Lea, 331.

Pope Alexander VIII
All sin is an offense against both God and Reason

In the Decree Sanctissimus of August 24, 1690, the Dijon thesis was condemned by Pope Alexander VIII, but it was not condemned as fully heretical, but rather as scandalous, rash, offensive to pious ears, and erroneous. Lea, 333. Thus stood condemned the following proposition:

Peccatum philosophicum seu morale est actus humanus disconvniens naturae rationalis et rectae ration; theologicum vero et morale est transgressio libera divinae legis. Philosophicum, quamvis grave, in illo, qui Deum vel ignorat vel de Deo actu non cogitat, est grave peccatum, sed non est offensa Dei, neque peccatum mortale dissolvens amicitiam Dei, neque aeterna poena dignum.

Philosophical or moral sin is a human act not in agreement with rational nature and right reason, theological and mortal sin is a free transgression of the Divine law. However grievous it may be, philosophical sin in one who is either ignorant of God or does not actually think of God, is indeed a grievous sin, but not an offense to God, nor a mortal sin dissolving friendship with God, nor worthy of eternal punishment.

It seems that the opposite then must be maintained, namely that sin can be offensive to God even if the sinner fails to know or does not consider God. So the Jesuit Viva argued that it is morally impossible that there is in any given man the ignorance of God and of the natural law so as to justify the notion of peccatum philosophicum, so that all violations of the natural law are ipso facto, even if implicitly, peccata theologica.** All sin is an offense against both God and reason.
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*Caramuelis Theologia Fundamentalis, Fund. XII. See Henry C. Lea, "Philosophical Sin" International Journal of Ethics (1895), 331 (herein Lea).
**Viva, Comment. in Prop. alteram Alexandri VIII, nn. 1, 12 (cited in Lea, 335). In his La Providence de Dieu, Cardinal Billot argued that since there is no philosophical sin, then if one is ignorant of God or does not advert to God one has no theological sin. But this is a "faulty interpretation" of the Alexandrine condemnation of the Dijon thesis. It is not that ignorance that an act is against the law of God qua God excuses from theological sin; rather, it is that any immoral act is necessarily theological, i.e., an offense against God, whether one is ignorant that an act is against the law of God or not. "If the interpretation is applied to one adversative it must hold for the other since both are included." Bertke, 884-86 & n. 10.