Sounds like the motto of my college newspaper, but actually they're the topics of the last three articles of ST I-II, 6, on the voluntary and the involuntary in relation to human acts.
In article 6, St. Thomas (following Aristotle and St. Gregory of Nyssa) teaches that things done through fear are essentially voluntary. Fear regards a future evil as something to be avoided, but we can only act in the here and now, when that future evil does not yet exist. Sailors who throw their cargo overboard in a storm do so voluntarily; given their knowledge, they genuinely wish to lighten the ship. Still, throwing their cargo overboard is contrary to their will apart from the circumstances of the storm, so he allows that acting through fear is involuntary in that respect.
In article 7, he says that, not only does concupiscence not cause involuntariness, but it makes things voluntary. Concupiscence causes us to desire evil things, thinking them good. The desire is real, even if the goodness of what is desired is not.
Article 8 introduces a threefold relationship between ignorance and the act of the will. An actor may be ignorant of something regarding his act voluntarily -- either because he wishes not to know or because he has chosen not to learn what he can and should know. If an actor weren't ignorant, he might still do what he's doing in ignorance. St. Thomas proposes the following relationships between ignorance and willing:
When an actor doesn't know he's doing what he's doing, but would still do it if he weren't ignorant, that's concomitant ignorance, and makes the act, not involuntary, but "non-voluntary," "since that which is unknown cannot be actually willed."
When an actor is voluntarily ignorant of something that, if he knew it, would cause him to act differently, that's consequent ignorance. Since the ignorance is voluntary, it can't make the act involuntary. (Except in respect of what would happen otherwise. This "voluntary simply, but involuntary in a certain respect" is similar to St. Thomas's treatment of fear in article 6; I usually see it talked about in terms of "culpable ignorance.") For what it's worth, St. Thomas distinguishes two kinds of consequent ignorance. One happens when you wish not to know something that, if you knew, would prevent you from doing something you want to do. This he calls "affected ignorance." The other, "ignorance of evil choice," happens when you will something without considering something you ought to consider before willing it; this, he says, can occur through some passion or habit, or simply because you never took the trouble to learn something you should have learned.
When an actor is not voluntarily ignorant, and would do something else if he weren't ignorant, it's antecedent ignorance and does cause involuntariness.
I think, though it doesn't say explicitly, that concommitance trumps consequence. That is, if an actor is unwittingly doing something he would wish to do if he knew he were doing it, then he can't be acting in voluntary ignorance, since he has no particular wish to be ignorant about it.
On the other hand, voluntary ignorance of things an actor can and should know broadens the scope of his ignorance, and so increases the chance he will unwittingly do something he would do even if he weren't ignorant. So a man who kills his enemy, thinking he is killing a deer, when he should have known he was killing his enemy, is guilty of imprudence but not murder.
UPDATED with a description of affected ignorance and ignorance of evil choice.