The Complete Aristotle (eng.)

elsewhere.

Book VI
    Translated by W. D. Ross
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    div id="section72" class="section" title="1">
1
    We are seeking the principles and the causes of the things that
are, and obviously of them qua being. For, while there is a cause
of health and of good condition, and the objects of mathematics
have first principles and elements and causes, and in general every
science which is ratiocinative or at all involves reasoning deals
with causes and principles, more or less precise, all these
sciences mark off some particular being-some genus, and inquire
into this, but not into being simply nor qua being, nor do they
offer any discussion of the essence of the things of which they
treat; but starting from the essence-some making it plain to the
senses, others assuming it as a hypothesis-they then demonstrate,
more or less cogently, the essential attributes of the genus with
which they deal. It is obvious, therefore, that such an induction
yields no demonstration of substance or of the essence, but some
other way of exhibiting it. And similarly the sciences omit the
question whether the genus with which they deal exists or does not
exist, because it belongs to the same kind of thinking to show what
it is and that it is.
    And since natural science, like other sciences, is in fact about
one class of being, i.e. to that sort of substance which has the
principle of its movement and rest present in itself, evidently it
is neither practical nor productive. For in the case of things made
the principle is in the maker-it is either reason or art or some
faculty, while in the case of things done it is in the doer-viz.
will, for that which is done and that which is willed are the same.
Therefore, if all thought is either practical or productive or
theoretical, physics must be a theoretical science, but it will
theorize about such being as admits of being moved, and about
substance-as-defined for the most part only as not separable from
matter. Now, we must not fail to notice the mode of being of the
essence and of its definition, for, without this, inquiry is but
idle. Of things defined, i.e. of ‘whats’, some are like ‘snub’, and
some like ‘concave’. And these differ because ‘snub’ is bound up
with matter (for what is snub is a concave nose), while concavity
is independent of perceptible matter. If then all natural things
are a analogous to the snub in their nature; e.g. nose, eye, face,
flesh, bone, and, in general, animal; leaf, root, bark, and, in
general, plant (for none of these can be defined without reference
to movement-they always have matter), it is clear how we must seek
and define the ‘what’ in the case of natural objects, and also that
it belongs to the student of nature to study even soul in a certain
sense, i.e. so much of it as is not independent of matter.
    That physics, then, is a theoretical science, is plain from
these considerations. Mathematics also, however, is theoretical;
but whether its objects are immovable and separable from matter, is
not at present clear; still, it is clear that some mathematical
theorems consider them qua immovable and qua separable from matter.
But if there is something which is eternal and immovable and
separable, clearly the knowledge of it belongs to a theoretical
science,-not, however, to physics (for physics deals with certain
movable things) nor to mathematics, but to a science prior to both.
For physics deals with things which exist separately but are not
immovable, and some parts of mathematics deal with things which are
immovable but presumably do not exist separately, but as embodied
in matter; while the first science deals with things which both
exist separately and are immovable. Now all causes must be eternal,
but especially these; for they are the causes that operate on so
much of the divine as appears to us. There must, then, be three
theoretical philosophies, mathematics, physics, and what we may
call theology, since it is obvious that if the divine is present
anywhere, it is present in things of this sort. And the highest
science must deal with the highest genus. Thus, while the
theoretical sciences are more to be desired than the other
sciences, this is more to be desired than the other theoretical
sciences. For one might raise the question whether first philosophy
is universal, or deals with one genus, i.e. some one kind of being;
for not even the mathematical sciences are all alike in this
respect,-geometry and astronomy deal with a certain particular