350 BC

                                    PHYSICS

                                  by Aristotle

                   translated by R. P. Hardie and R. K. Gaye

                              Book I

                                 1

  WHEN the objects of an inquiry, in any department, have
principles, conditions, or elements, it is through acquaintance with
these that knowledge, that is to say scientific knowledge, is
attained. For we do not think that we know a thing until we are
acquainted with its primary conditions or first principles, and have
carried our analysis as far as its simplest elements. Plainly
therefore in the science of Nature, as in other branches of study, our
first task will be to try to determine what relates to its principles.

  The natural way of doing this is to start from the things which
are more knowable and obvious to us and proceed towards those which
are clearer and more knowable by nature; for the same things are not
'knowable relatively to us' and 'knowable' without qualification. So
in the present inquiry we must follow this method and advance from
what is more obscure by nature, but clearer to us, towards what is
more clear and more knowable by nature.

  Now what is to us plain and obvious at first is rather confused
masses, the elements and principles of which become known to us
later by analysis. Thus we must advance from generalities to
particulars; for it is a whole that is best known to sense-perception,
and a generality is a kind of whole, comprehending many things
within it, like parts. Much the same thing happens in the relation
of the name to the formula. A name, e.g. 'round', means vaguely a sort
of whole: its definition analyses this into its particular senses.
Similarly a child begins by calling all men 'father', and all women
'mother', but later on distinguishes each of them.

                                 2

  The principles in question must be either (a) one or (b) more than
one. If (a) one, it must be either (i) motionless, as Parmenides and
Melissus assert, or (ii) in motion, as the physicists hold, some
declaring air to be the first principle, others water. If (b) more
than one, then either (i) a finite or (ii) an infinite plurality. If
(i) finite (but more than one), then either two or three or four or
some other number. If (ii) infinite, then either as Democritus
believed one in kind, but differing in shape or form; or different
in kind and even contrary.

  A similar inquiry is made by those who inquire into the number of
existents: for they inquire whether the ultimate constituents of
existing things are one or many, and if many, whether a finite or an
infinite plurality. So they too are inquiring whether the principle or
element is one or many.

  Now to investigate whether Being is one and motionless is not a
contribution to the science of Nature. For just as the geometer has
nothing more to say to one who denies the principles of his
science-this being a question for a different science or for or common
to all-so a man investigating principles cannot argue with one who
denies their existence. For if Being is just one, and one in the way
mentioned, there is a principle no longer, since a principle must be
the principle of some thing or things.

  To inquire therefore whether Being is one in this sense would be
like arguing against any other position maintained for the sake of
argument (such as the Heraclitean thesis, or such a thesis as that
Being is one man) or like refuting a merely contentious argument-a
description which applies to the arguments both of Melissus and of
Parmenides: their premisses are false and their conclusions do not
follow. Or rather the argument of Melissus is gross and palpable and
offers no difficulty at all: accept one ridiculous proposition and the
rest follows-a simple enough proceeding.

  We physicists, on the other hand, must take for granted that the
things that exist by nature are, either all or some of them, in motion
which is indeed made plain by induction. Moreover, no man of science
is bound to solve every kind of difficulty that may be raised, but
only as many as are drawn falsely from the principles of the
science: it is not our business to refute those that do not arise in
this way: just as it is the duty of the geometer to refute the
squaring of the circle by means of segments, but it is not his duty to
refute Antiphon's proof. At the same time the holders of the theory of
which we are speaking do incidentally raise physical questions, though
Nature is not their subject: so it will perhaps be as well to spend
a few words on them, especially as the inquiry is not without
scientific interest.

  The most pertinent question with which to begin will be this: In
what sense is it asserted that all things are one? For 'is' is used in
many senses. Do they mean that all things 'are' substance or
quantities or qualities? And, further, are all things one
substance-one man, one horse, or one soul-or quality and that one
and the same-white or hot or something of the kind? These are all very
different doctrines and all impossible to maintain.

  For if both substance and quantity and quality are, then, whether