Thomas Aquinas

“ A direct cause is one that moves by its own power, as the generator is the moving cause of heavy and light things. An indirect cause, is either one that removes an impediment, or the removal itself of an impediment: and it is in this way that ignorance can be the cause of a sinful act; because it is a privation of knowledge perfecting the reason that forbids the act of sin, in so far as it directs human acts. ”

“ If, however, the ignorance be such as to be entirely involuntary, either through being invincible, or through being of matters one is not bound to know, then such like ignorance excuses from sin altogether. ”

“ Now we must observe that the reason directs human acts in accordance with a twofold knowledge, universal and particular: because in conferring about what is to be done, it employs a syllogism, the conclusion of which is an act of judgment, or of choice, or an operation. ”

“ Just as in a sin of transgression, the sin consists not only in the act of the will, but also in the act willed, which is commanded by the will; so in a sin of omission not only the act of the will is a sin, but also the omission, in so far as it is in some way voluntary ”

“ Some of these we are under an obligation to know, those, to wit, without the knowledge of which we are unable to accomplish a due act rightly. Wherefore all are bound in common to know the articles of faith, and the universal principles of right, and each individual is bound to know matters regarding his duty or state. Meanwhile there are other things which a man may have a natural aptitude to know, yet he is not bound to know them, such as the geometrical theorems, and contingent particulars, except in some individual case. ”

“ But a singular proposition does not follow from a universal proposition, except through the medium of a particular proposition: thus a man is restrained from an act of parricide, by the knowledge that it is wrong to kill one's father, and that this man is his father. ”

“ It might also be said that the words quoted refer to an ordinance of the legislator named Pittacus, who ordered drunkards to be more severely punished if they assaulted anyone; having an eye, not to the indulgence which the drunkard might claim, but to expediency, since more harm is done by the drunk than by the sober, as the Philosopher observes (Polit. ii) . ”