The Complete Aristotle (eng.)

consists cannot be defined, since a
definitory formula predicates something of something, and one part
of the definition must play the part of matter and the other that
of form.
    It is also obvious that, if substances are in a sense numbers,
they are so in this sense and not, as some say, as numbers of
units. For a definition is a sort of number; for (1) it is
divisible, and into indivisible parts (for definitory formulae are
not infinite), and number also is of this nature. And (2) as, when
one of the parts of which a number consists has been taken from or
added to the number, it is no longer the same number, but a
different one, even if it is the very smallest part that has been
taken away or added, so the definition and the essence will no
longer remain when anything has been taken away or added. And (3)
the number must be something in virtue of which it is one, and this
these thinkers cannot state, what makes it one, if it is one (for
either it is not one but a sort of heap, or if it is, we ought to
say what it is that makes one out of many); and the definition is
one, but similarly they cannot say what makes it one. And this is a
natural result; for the same reason is applicable, and substance is
one in the sense which we have explained, and not, as some say, by
being a sort of unit or point; each is a complete reality and a
definite nature. And (4) as number does not admit of the more and
the less, neither does substance, in the sense of form, but if any
substance does, it is only the substance which involves matter. Let
this, then, suffice for an account of the generation and
destruction of so-called substances in what sense it is possible
and in what sense impossible—and of the reduction of things to
number.
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4
    Regarding material substance we must not forget that even if all
things come from the same first cause or have the same things for
their first causes, and if the same matter serves as starting-point
for their generation, yet there is a matter proper to each, e.g.
for phlegm the sweet or the fat, and for bile the bitter, or
something else; though perhaps these come from the same original
matter. And there come to be several matters for the same thing,
when the one matter is matter for the other; e.g. phlegm comes from
the fat and from the sweet, if the fat comes from the sweet; and it
comes from bile by analysis of the bile into its ultimate matter.
For one thing comes from another in two senses, either because it
will be found at a later stage, or because it is produced if the
other is analysed into its original constituents. When the matter
is one, different things may be produced owing to difference in the
moving cause; e.g. from wood may be made both a chest and a bed.
But some different things must have their matter different; e.g. a
saw could not be made of wood, nor is this in the power of the
moving cause; for it could not make a saw of wool or of wood. But
if, as a matter of fact, the same thing can be made of different
material, clearly the art, i.e. the moving principle, is the same;
for if both the matter and the moving cause were different, the
product would be so too.
    When one inquires into the cause of something, one should, since
‘causes’ are spoken of in several senses, state all the possible
causes. what is the material cause of man? Shall we say ‘the
menstrual fluid’? What is moving cause? Shall we say ‘the seed’?
The formal cause? His essence. The final cause? His end. But
perhaps the latter two are the same.-It is the proximate causes we
must state. What is the material cause? We must name not fire or
earth, but the matter peculiar to the thing.
    Regarding the substances that are natural and generable, if the
causes are really these and of this number and we have to learn the
causes, we must inquire thus, if we are to inquire rightly. But in
the case of natural but eternal substances another account must be
given. For perhaps some have no matter, or not matter of this sort
but only such as can be moved in respect of place. Nor does matter
belong to those things which exist by nature but are not
substances; their substratum is the substance. E.g what is the
cause of eclipse? What is its matter? There is none; the moon is
that which suffers eclipse. What is the moving cause which
extinguished the light? The earth. The final cause perhaps does not
exist. The formal principle is the definitory formula, but this is
obscure