 Consequently, [in the above case] a right act of the will and an error of the intellect remain at the same time with respect to the same object. And the whole reason is because that error is not in the power of the one who is mistaken, who took all due diligence to find out the truth, and therefore that error excuses from every sin. And consequently, the will that elicits the act in conformity to such [invincibly] erroneous reason acts virtuously and meritoriously. Indeed, had he not, while in such error, willed to help that person, he would have performed a vicious and demeritorious act because such an act would have been knowingly elicited against conscience and against non-culpable reason, because in the aforementioned case he does not know that he is in error but believes that he possesses right reason, and consequently by despising reason [in this way] he sins mortally. (Quaestiones varie q. 8, a. 2, Oth 8: 423–424)