Physics   

Some identify the nature or substance of a natural object with that
immediate constituent of it which taken by itself is without
arrangement, e.g. the wood is the 'nature' of the bed, and the bronze
the 'nature' of the statue.
As an indication of this Antiphon points out that if you planted a bed
and the rotting wood acquired the power of sending up a shoot, it
would not be a bed that would come up, but wood-which shows that the
arrangement in accordance with the rules of the art is merely an
incidental attribute, whereas the real nature is the other, which,
further, persists continuously through the process of making.
But if the material of each of these objects has itself the same
relation to something else, say bronze (or gold) to water, bones (or
wood) to earth and so on, that (they say) would be their nature and
essence. Consequently some assert earth, others fire or air or water
or some or all of these, to be the nature of the things that are. For
whatever any one of them supposed to have this character-whether one
thing or more than one thing-this or these he declared to be the whole
of substance, all else being its affections, states, or dispositions.
Every such thing they held to be eternal (for it could not pass into
anything else), but other things to come into being and cease to be
times without number.
This then is one account of 'nature', namely that it is the immediate
material substratum of things which have in themselves a principle of
motion or change.
Another account is that 'nature' is the shape or form which is
specified in the definition of the thing.
For the word 'nature' is applied to what is according to nature and
the natural in the same way as 'art' is applied to what is artistic or
a work of art. We should not say in the latter case that there is
anything artistic about a thing, if it is a bed only potentially, not
yet having the form of a bed; nor should we call it a work of art. The
same is true of natural compounds. What is potentially flesh or bone
has not yet its own 'nature', and does not exist until it receives the
form specified in the definition, which we name in defining what flesh
or bone is. Thus in the second sense of 'nature' it would be the shape
or form (not separable except in statement) of things which have in
themselves a source of motion. (The combination of the two, e.g. man,
is not 'nature' but 'by nature' or 'natural'.)
The form indeed is 'nature' rather than the matter; for a thing is
more properly said to be what it is when it has attained to fulfilment
than when it exists potentially. Again man is born from man, but not
bed from bed. That is why people say that the figure is not the nature
of a bed, but the wood is-if the bed sprouted not a bed but wood would
come up. But even if the figure is art, then on the same principle the
shape of man is his nature. For man is born from man.
We also speak of a thing's nature as being exhibited in the process of
growth by which its nature is attained. The 'nature' in this sense is
not like 'doctoring', which leads not to the art of doctoring but to
health. Doctoring must start from the art, not lead to it. But it is
not in this way that nature (in the one sense) is related to nature
(in the other). What grows qua growing grows from something into
something. Into what then does it grow? Not into that from which it
arose but into that to which it tends. The shape then is nature.
'Shape' and 'nature', it should be added, are in two senses. For the
privation too is in a way form. But whether in unqualified coming to
be there is privation, i.e. a contrary to what comes to be, we must
consider later.
Part 2
We have distinguished, then, the different ways in which the term
'nature' is used.
The next point to consider is how the mathematician differs from the
physicist. Obviously physical bodies contain surfaces and volumes,
lines and points, and these are the subject-matter of mathematics.
Further, is astronomy different from physics or a department of it? It