The Complete Aristotle (eng.)

voluntariness be not present as well.
By the voluntary I mean, as has been said before, any of the things
in a man’s own power which he does with knowledge, i.e. not in
ignorance either of the person acted on or of the instrument used
or of the end that will be attained (e.g. whom he is striking, with
what, and to what end), each such act being done not incidentally
nor under compulsion (e.g. if A takes B’s hand and therewith
strikes C, B does not act voluntarily; for the act was not in his
own power). The person struck may be the striker’s father, and the
striker may know that it is a man or one of the persons present,
but not know that it is his father; a similar distinction may be
made in the case of the end, and with regard to the whole action.
Therefore that which is done in ignorance, or though not done in
ignorance is not in the agent’s power, or is done under compulsion,
is involuntary (for many natural processes, even, we knowingly both
perform and experience, none of which is either voluntary or
involuntary; e.g. growing old or dying). But in the case of unjust
and just acts alike the injustice or justice may be only
incidental; for a man might return a deposit unwillingly and from
fear, and then he must not be said either to do what is just or to
act justly, except in an incidental way. Similarly the man who
under compulsion and unwillingly fails to return the deposit must
be said to act unjustly, and to do what is unjust, only
incidentally. Of voluntary acts we do some by choice, others not by
choice; by choice those which we do after deliberation, not by
choice those which we do without previous deliberation. Thus there
are three kinds of injury in transactions between man and man;
those done in ignorance are mistakes when the person acted on, the
act, the instrument, or the end that will be attained is other than
the agent supposed; the agent thought either that he was not hiting
any one or that he was not hitting with this missile or not hitting
this person or to this end, but a result followed other than that
which he thought likely (e.g. he threw not with intent to wound but
only to prick), or the person hit or the missile was other than he
supposed. Now when (1) the injury takes place contrary to
reasonable expectation, it is a misadventure. When (2) it is not
contrary to reasonable expectation, but does not imply vice, it is
a mistake (for a man makes a mistake when the fault originates in
him, but is the victim of accident when the origin lies outside
him). When (3) he acts with knowledge but not after deliberation,
it is an act of injustice-e.g. the acts due to anger or to other
passions necessary or natural to man; for when men do such harmful
and mistaken acts they act unjustly, and the acts are acts of
injustice, but this does not imply that the doers are unjust or
wicked; for the injury is not due to vice. But when (4) a man acts
from choice, he is an unjust man and a vicious man.
    Hence acts proceeding from anger are rightly judged not to be
done of malice aforethought; for it is not the man who acts in
anger but he who enraged him that starts the mischief. Again, the
matter in dispute is not whether the thing happened or not, but its
justice; for it is apparent injustice that occasions rage. For they
do not dispute about the occurrence of the act-as in commercial
transactions where one of the two parties must be vicious-unless
they do so owing to forgetfulness; but, agreeing about the fact,
they dispute on which side justice lies (whereas a man who has
deliberately injured another cannot help knowing that he has done
so), so that the one thinks he is being treated unjustly and the
other disagrees.
    But if a man harms another by choice, he acts unjustly; and
these are the acts of injustice which imply that the doer is an
unjust man, provided that the act violates proportion or equality.
Similarly, a man is just when he acts justly by choice; but he acts
justly if he merely acts voluntarily.
    Of involuntary acts some are excusable, others not. For the
mistakes which men make not only in ignorance but also from
ignorance are excusable, while those which men do not from
ignorance but (though they do them in ignorance) owing to a passion
which is neither natural nor such as man is liable to, are not
excusable.
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9
    Assuming that we have sufficiently defined the suffering and
doing of injustice, it may be asked (1) whether the truth in
expressed in