movement come? The whole study of nature has been annihilated.
And what is thought to be easy-to show that all things are
one-is not done; for what is proved by the method of setting out
instances is not that all things are one but that there is a One
itself,-if we grant all the assumptions. And not even this follows, if
we do not grant that the universal is a genus; and this in some
cases it cannot be.
Nor can it be explained either how the lines and planes and solids
that come after the numbers exist or can exist, or what significance
they have; for these can neither be Forms (for they are not
numbers), nor the intermediates (for those are the objects of
mathematics), nor the perishable things. This is evidently a
distinct fourth class.
In general, if we search for the elements of existing things
without distinguishing the many senses in which things are said to
exist, we cannot find them, especially if the search for the
elements of which things are made is conducted in this manner. For
it is surely impossible to discover what 'acting' or 'being acted on',
or 'the straight', is made of, but if elements can be discovered at
all, it is only the elements of substances; therefore either to seek
the elements of all existing things or to think one has them is
And how could we learn the elements of all things? Evidently we
cannot start by knowing anything before. For as he who is learning
geometry, though he may know other things before, knows none of the
things with which the science deals and about which he is to learn, so
is it in all other cases. Therefore if there is a science of all
things, such as some assert to exist, he who is learning this will
know nothing before. Yet all learning is by means of premisses which
are (either all or some of them) known before,-whether the learning be
by demonstration or by definitions; for the elements of the definition
must be known before and be familiar; and learning by induction
proceeds similarly. But again, if the science were actually innate, it
were strange that we are unaware of our possession of the greatest
Again, how is one to come to know what all things are made of, and
how is this to be made evident? This also affords a difficulty; for
there might be a conflict of opinion, as there is about certain
syllables; some say za is made out of s and d and a, while others
say it is a distinct sound and none of those that are familiar.
Further, how could we know the objects of sense without having the
sense in question? Yet we ought to, if the elements of which all
things consist, as complex sounds consist of the clements proper to
sound, are the same.
It is evident, then, even from what we have said before, that
all men seem to seek the causes named in the Physics, and that we
cannot name any beyond these; but they seek these vaguely; and
though in a sense they have all been described before, in a sense they
have not been described at all. For the earliest philosophy is, on all
subjects, like one who lisps, since it is young and in its beginnings.
For even Empedocles says bone exists by virtue of the ratio in it. Now
this is the essence and the substance of the thing. But it is
similarly necessary that flesh and each of the other tissues should be
the ratio of its elements, or that not one of them should; for it is
on account of this that both flesh and bone and everything else will
exist, and not on account of the matter, which he names,-fire and
earth and water and air. But while he would necessarily have agreed if
another had said this, he has not said it clearly.
On these questions our views have been expressed before; but let
us return to enumerate the difficulties that might be raised on
these same points; for perhaps we may get from them some help
towards our later difficulties.