that we perform or undergo knowingly, though none
of them is either voluntary or involuntary1
; for example, growing old, and
Also an act may be either just or unjust incidentally. A man may restore a deposit
unwillingly and from fear of consequences, and we must not then say that he does a just
act, nor that he acts justly, except incidentally; and similarly a man who under
compulsion and against his will fails to restore a deposit can only be said to act
unjustly or do what is unjust incidentally.
Again voluntary acts are divided into acts done by choice and those done not by choice,
the former being those done after deliberation and the latter those done without previous
There are then three ways2
in which a man may injure his fellow. An injury done in ignorance is an error, the person
affected or the act or the instrument or the result being other than the agent supposed;
for example, he did not think to hit, or not with this missile, or not this person, or not
with this result, but it happened that either the result was other than he expected
（for instance he did not mean to inflict a wound but only a prick）, or
the person, or the missile.
When then the injury happens
contrary to reasonable expectation, it is （1） a misadventure. When,
though not contrary to reasonable expectation, it is done without evil intent, it is
（2） a culpable error; for an error is culpable when the cause of one's
ignorance lies in oneself, but only a misadventure when the cause lies outside oneself.