actually. We have said in our account of substance that everything
that is produced is something produced from something and by
something, and that the same in species as it.
This is why it is thought impossible to be a builder if one has
built nothing or a harper if one has never played the harp; for he who
learns to play the harp learns to play it by playing it, and all other
learners do similarly. And thence arose the sophistical quibble,
that one who does not possess a science will be doing that which is
the object of the science; for he who is learning it does not
possess it. But since, of that which is coming to be, some part must
have come to be, and, of that which, in general, is changing, some
part must have changed (this is shown in the treatise on movement), he
who is learning must, it would seem, possess some part of the science.
But here too, then, it is clear that actuality is in this sense
also, viz. in order of generation and of time, prior to potency.
But (3) it is also prior in substantiality; firstly, (a) because
the things that are posterior in becoming are prior in form and in
substantiality (e.g. man is prior to boy and human being to seed;
for the one already has its form, and the other has not), and
because everything that comes to be moves towards a principle, i.e. an
end (for that for the sake of which a thing is, is its principle,
and the becoming is for the sake of the end), and the actuality is the
end, and it is for the sake of this that the potency is acquired.
For animals do not see in order that they may have sight, but they
have sight that they may see. And similarly men have the art of
building that they may build, and theoretical science that they may
theorize; but they do not theorize that they may have theoretical
science, except those who are learning by practice; and these do not
theorize except in a limited sense, or because they have no need to
theorize. Further, matter exists in a potential state, just because it
may come to its form; and when it exists actually, then it is in its
form. And the same holds good in all cases, even those in which the
end is a movement. And so, as teachers think they have achieved
their end when they have exhibited the pupil at work, nature does
likewise. For if this is not the case, we shall have Pauson's Hermes
over again, since it will be hard to say about the knowledge, as about
the figure in the picture, whether it is within or without. For the
action is the end, and the actuality is the action. And so even the
word 'actuality' is derived from 'action', and points to the
And while in some cases the exercise is the ultimate thing (e.g.
in sight the ultimate thing is seeing, and no other product besides
this results from sight), but from some things a product follows (e.g.
from the art of building there results a house as well as the act of
building), yet none the less the act is in the former case the end and
in the latter more of an end than the potency is. For the act of
building is realized in the thing that is being built, and comes to
be, and is, at the same time as the house.
Where, then, the result is something apart from the exercise,
the actuality is in the thing that is being made, e.g. the act of
building is in the thing that is being built and that of weaving in
the thing that is being woven, and similarly in all other cases, and
in general the movement is in the thing that is being moved; but where
there is no product apart from the actuality, the actuality is present
in the agents, e.g. the act of seeing is in the seeing subject and
that of theorizing in the theorizing subject and the life is in the
soul (and therefore well-being also; for it is a certain kind of
Obviously, therefore, the substance or form is actuality.
According to this argument, then, it is obvious that actuality is
prior in substantial being to potency; and as we have said, one
actuality always precedes another in time right back to the
actuality of the eternal prime mover.
But (b) actuality is prior in a stricter sense also; for eternal