Physics   

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.
Part 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