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.
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 seems absurd that the physicist should be supposed to know
the nature of sun or moon, but not to know any of their essential
attributes, particularly as the writers on physics obviously do
discuss their shape also and whether the earth and the world are
spherical or not.
Now the mathematician, though he too treats of these things,
nevertheless does not treat of them as the limits of a physical
body; nor does he consider the attributes indicated as the
attributes of such bodies. That is why he separates them; for in
thought they are separable from motion, and it makes no difference,
nor does any falsity result, if they are separated. The holders of the
theory of Forms do the same, though they are not aware of it; for they
separate the objects of physics, which are less separable than those
of mathematics. This becomes plain if one tries to state in each of
the two cases the definitions of the things and of their attributes.
'Odd' and 'even', 'straight' and 'curved', and likewise 'number',
'line', and 'figure', do not involve motion; not so 'flesh' and 'bone'
and 'man'-these are defined like 'snub nose', not like 'curved'.
Similar evidence is supplied by the more physical of the branches of
mathematics, such as optics, harmonics, and astronomy. These are in
a way the converse of geometry. While geometry investigates physical
lines but not qua physical, optics investigates mathematical lines,
but qua physical, not qua mathematical.
Since 'nature' has two senses, the form and the matter, we must
investigate its objects as we would the essence of snubness. That
is, such things are neither independent of matter nor can be defined
in terms of matter only. Here too indeed one might raise a difficulty.
Since there are two natures, with which is the physicist concerned? Or
should he investigate the combination of the two? But if the
combination of the two, then also each severally. Does it belong
then to the same or to different sciences to know each severally?
If we look at the ancients, physics would to be concerned with the
matter. (It was only very slightly that Empedocles and Democritus
touched on the forms and the essence.)
But if on the other hand art imitates nature, and it is the part
of the same discipline to know the form and the matter up to a point
(e.g. the doctor has a knowledge of health and also of bile and
phlegm, in which health is realized, and the builder both of the
form of the house and of the matter, namely that it is bricks and
also to know nature in both its senses.
Again, 'that for the sake of which', or the end, belongs to the same
department of knowledge as the means. But the nature is the end or
'that for the sake of which'. For if a thing undergoes a continuous
change and there is a stage which is last, this stage is the end or
'that for the sake of which'. (That is why the poet was carried away
into making an absurd statement when he said 'he has the end for the
sake of which he was born'. For not every stage that is last claims to
be an end, but only that which is best.)
For the arts make their material (some simply 'make' it, others make
it serviceable), and we use everything as if it was there for our
sake. (We also are in a sense an end. 'That for the sake of which' has
two senses: the distinction is made in our work On Philosophy.) The
arts, therefore, which govern the matter and have knowledge are two,
namely the art which uses the product and the art which directs the
production of it. That is why the using art also is in a sense
directive; but it differs in that it knows the form, whereas the art
which is directive as being concerned with production knows the
matter. For the helmsman knows and prescribes what sort of form a helm
should have, the other from what wood it should be made and by means
of what operations. In the products of art, however, we make the
material with a view to the function, whereas in the products of
nature the matter is there all along.
Again, matter is a relative term: to each form there corresponds a
special matter. How far then must the physicist know the form or
essence? Up to a point, perhaps, as the doctor must know sinew or
the smith bronze (i.e. until he understands the purpose of each):
and the physicist is concerned only with things whose forms are
separable indeed, but do not exist apart from matter. Man is
begotten by man and by the sun as well. The mode of existence and
essence of the separable it is the business of the primary type of
philosophy to define.
3
Now that we have established these distinctions, we must proceed
to consider causes, their character and number. Knowledge is the
object of our inquiry, and men do not think they know a thing till
they have grasped the 'why' of (which is to grasp its primary
cause). So clearly we too must do this as regards both coming to be
and passing away and every kind of physical change, in order that,
knowing their principles, we may try to refer to these principles each
of our problems.
In one sense, then, (1) that out of which a thing comes to be and
which persists, is called 'cause', e.g. the bronze of the statue,
the silver of the bowl, and the genera of which the bronze and the
silver are species.
In another sense (2) the form or the archetype, i.e. the statement
of the essence, and its genera, are called 'causes' (e.g. of
the
octave the relation of 2:1, and generally number), and the parts in
the definition.
Again (3) the primary source of the change or coming to rest; e.g.
the man who gave advice is a cause, the father is cause of the
child, and generally what makes of what is made and what causes change
of what is changed.
Again (4) in the sense of end or 'that for the sake of which' a
thing is done, e.g. health is the cause of walking about. ('Why is
he walking about?' we say. 'To be healthy', and, having said that,
we think we have assigned the cause.) The same is true also of all the
intermediate steps which are brought about through the action of
something else as means towards the end, e.g. reduction of flesh,
purging, drugs, or surgical instruments are means towards health.
All these things are 'for the sake of' the end, though they differ
from one another in that some are activities, others instruments.
This then perhaps exhausts the number of ways in which the term
'cause' is used.
As the word has several senses, it follows that there are several
causes of the same thing not merely in virtue of a concomitant
attribute), e.g. both the art of the sculptor and the bronze are
causes of the statue. These are causes of the statue qua statue, not
in virtue of anything else that it may be-only not in the same way,
the one being the material cause, the other the cause whence the
motion comes. Some things cause each other reciprocally, e.g. hard
work causes fitness and vice versa, but again not in the same way, but
the one as end, the other as the origin of change. Further the same
thing is the cause of contrary results. For that which by its presence
brings about one result is sometimes blamed for bringing about the
contrary by its absence. Thus we ascribe the wreck of a ship to the
absence of the pilot whose presence was the cause of its safety.
All the causes now mentioned fall into four familiar divisions.
The letters are the causes of syllables, the material of artificial
products, fire, c., of bodies, the parts of the whole, and the
premisses of the conclusion, in the sense of 'that from which'. Of
these pairs the one set are causes in the sense of substratum, e.g.
the parts, the other set in the sense of essence-the whole and the
combination and the form. But the seed and the doctor and the adviser,
and generally the maker, are all sources whence the change or
stationariness originates, while the others are causes in the sense of
the end or the good of the rest; for 'that for the sake of which'
means what is best and the end of the things that lead up to it.
(Whether we say the 'good itself or the 'apparent good' makes no
difference.)
Such then is the number and nature of the kinds of cause.
Now the modes of causation are many, though when brought under heads
they too can be reduced in number. For 'cause' is used in many
senses and even within the same kind one may be prior to another (e.g.
the doctor and the expert are causes of health, the relation 2:1 and
number of the octave), and always what is inclusive to what is
particular. Another mode of causation is the incidental and its
genera, e.g. in one way 'Polyclitus', in another 'sculptor' is the
cause of a statue, because 'being Polyclitus' and 'sculptor' are
incidentally conjoined. Also the classes in which the incidental
attribute is included; thus 'a man' could be said to be the cause of a
statue or, generally, 'a living creature'. An incidental attribute too
may be more or less remote, e.g. suppose that 'a pale man' or 'a
musical man' were said to be the cause of the statue.
All causes, both proper and incidental, may be spoken of either as
potential or as actual; e.g. the cause of a house being built is
either 'house-builder' or 'house-builder building'.
Similar distinctions can be made in the things of which the causes
are causes, e.g. of 'this statue' or of 'statue' or of 'image'
generally, of 'this bronze' or of 'bronze' or of 'material' generally.
So too with the incidental attributes. Again we may use a complex
expression for either and say, e.g. neither 'Polyclitus' nor
'sculptor' but 'Polyclitus, sculptor'.
All these various uses, however, come to six in number, under each
of which again the usage is twofold. Cause means either what is
particular or a genus, or an incidental attribute or a genus of
that, and these either as a complex or each by itself; and all six
either as actual or as potential. The difference is this much, that
causes which are actually at work and particular exist and cease to
exist simultaneously with their effect, e.g. this healing person
with this being-healed person and that house-building man with that
being-built house; but this is not always true of potential
causes--the house and the housebuilder do not pass away
simultaneously.
In investigating the cause of each thing it is always necessary to
seek what is most precise (as also in other things): thus man builds
because he is a builder, and a builder builds in virtue of his art
of building. This last cause then is prior: and so generally.
Further, generic effects should be assigned to generic causes,
particular effects to particular causes, e.g. statue to sculptor, this
statue to this sculptor; and powers are relative to possible
effects, actually operating causes to things which are actually
being effected.
This must suffice for our account of the number of causes and the
modes of causation.
4
But chance also and spontaneity are reckoned among causes: many
things are said both to be and to come to be as a result of chance and
spontaneity. We must inquire therefore in what manner chance and
spontaneity are present among the causes enumerated, and whether
they are the same or different, and generally what chance and
spontaneity are.
Some people even question whether they are real or not. They say
that nothing happens by chance, but that everything which we ascribe
to chance or spontaneity has some definite cause, e.g. coming 'by
chance' into the market and finding there a man whom one wanted but
did not expect to meet is due to one's wish to go and buy in the
market. Similarly in other cases of chance it is always possible, they
maintain, to find something which is the cause; but not chance, for if
chance were real, it would seem strange indeed, and the question might
be raised, why on earth none of the wise men of old in speaking of the
causes of generation and decay took account of chance; whence it would
seem that they too did not believe that anything is by chance. But
there is a further circumstance that is surprising. Many things both
come to be and are by chance and spontaneity, and although know that
each of them can be ascribed to some cause (as the old argument said
which denied chance), nevertheless they speak of some of these
things as happening by chance and others not. For this reason also
they ou
ght to have at least referred to the matter in some way or
other.
Certainly the early physicists found no place for chance among the
causes which they recognized-love, strife, mind, fire, or the like.
This is strange, whether they supposed that there is no such thing
as chance or whether they thought there is but omitted to mention
it-and that too when they sometimes used it, as Empedocles does when
he says that the air is not always separated into the highest
region, but 'as it may chance'. At any rate he says in his cosmogony
that 'it happened to run that way at that time, but it often ran
otherwise.' He tells us also that most of the parts of animals came to
be by chance.
There are some too who ascribe this heavenly sphere and all the
worlds to spontaneity. They say that the vortex arose spontaneously,
i.e. the motion that separated and arranged in its present order all
that exists. This statement might well cause surprise. For they are
asserting that chance is not responsible for the existence or
generation of animals and plants, nature or mind or something of the
kind being the cause of them (for it is not any chance thing that
comes from a given seed but an olive from one kind and a man from
another); and yet at the same time they assert that the heavenly
sphere and the divinest of visible things arose spontaneously,
having no such cause as is assigned to animals and plants. Yet if this
is so, it is a fact which deserves to be dwelt upon, and something
might well have been said about it. For besides the other
absurdities of the statement, it is the more absurd that people should
make it when they see nothing coming to be spontaneously in the
heavens, but much happening by chance among the things which as they
say are not due to chance; whereas we should have expected exactly the
opposite.