Nicomachean Ethics

Now every action of which ignorance is the cause is not-voluntary, but that only is involuntary which is attended with pain and remorse; for clearly the man who has done anything by reason of ignorance, but is not annoyed at his own action, cannot be said to have done it his will because he did not know he was doing it, nor again his will because he is not sorry for it.

So then of the class “acting by reason of ignorance,” he who feels regret afterwards is thought to be an involuntary agent, and him that has no such feeling, since he certainly is different from the other, we will call a not-voluntary agent; for as there is a real difference it is better to have a proper name.

Again, there seems to be a difference between acting ignorance and acting ignorance: for instance, we do not usually assign ignorance as the cause of the actions of the drunken or angry man, but either the drunkenness or the anger, yet they act not knowingly but with ignorance.

Again, every bad man is ignorant what he ought to do and what to leave undone, and by reason of such error men become unjust and wholly evil.

Again, we do not usually apply the term involuntary when a man is ignorant of his own true interest;[2] because ignorance which affects moral choice[3] constitutes depravity but not involuntariness: nor does any ignorance of principle (because for this men are blamed) but ignorance in particular details, wherein consists the action and wherewith it is concerned, for in these there is both compassion and allowance, because he who acts in ignorance of any of them acts in a proper sense involuntarily.

It may be as well, therefore, to define these particular details; what they are, and how many; viz. who acts, what he is doing, with respect to what or in what, sometimes with what, as with what instrument, and with what result;[4] as that of preservation, for instance, and how, as whether softly or violently.

All these particulars, in one and the same case, no man in his senses could be ignorant of; plainly not of the agent, being himself. But what he is doing a man may be ignorant, as men in speaking say a thing escaped them unawares; or as Aeschylus did with respect to the Mysteries, that he was not aware that it was unlawful to speak of them; or as in the case of that catapult accident the other day the man said he discharged it merely to display its operation. Or a person might suppose a son to be an enemy, as Merope did; or that the spear really pointed was rounded off; or that the stone was a pumice; or in striking with a view to save might kill; or might strike when merely wishing to show another, as people do in sham-fighting.

Now since ignorance is possible in respect to all these details in which the action consists, he that acted in ignorance of any of them is thought to have acted involuntarily, and he most so who was in ignorance as regards the most important, which are thought to be those in which the action consists, and the result.

Further, not only must the ignorance be of this kind, to constitute an action involuntary, but it must be also understood that the action is followed by pain and regret.