Physics   

fortunate because they are held in honour, while their fellows are
trodden under foot. Even these things, however, can in a way be
affected by chance, when one who is dealing with them does something
to them by chance, but not otherwise.
The spontaneous on the other hand is found both in the lower animals
and in many inanimate objects. We say, for example, that the horse
came 'spontaneously', because, though his coming saved him, he did not
come for the sake of safety. Again, the tripod fell 'of itself',
because, though when it fell it stood on its feet so as to serve for a
seat, it did not fall for the sake of that.
Hence it is clear that events which (1) belong to the general class of
things that may come to pass for the sake of something, (2) do not
come to pass for the sake of what actually results, and (3) have an
external cause, may be described by the phrase 'from spontaneity'.
These 'spontaneous' events are said to be 'from chance' if they have
the further characteristics of being the objects of deliberate
intention and due to agents capable of that mode of action. This is
indicated by the phrase 'in vain', which is used when A which is for
the sake of B, does not result in B. For instance, taking a walk is
for the sake of evacuation of the bowels; if this does not follow
after walking, we say that we have walked 'in vain' and that the
walking was 'vain'. This implies that what is naturally the means to
an end is 'in vain', when it does not effect the end towards which it
was the natural means-for it would be absurd for a man to say that he
had bathed in vain because the sun was not eclipsed, since the one was
not done with a view to the other. Thus the spontaneous is even
according to its derivation the case in which the thing itself happens
in vain. The stone that struck the man did not fall for the purpose of
striking him; therefore it fell spontaneously, because it might have
fallen by the action of an agent and for the purpose of striking. The
difference between spontaneity and what results by chance is greatest
in things that come to be by nature; for when anything comes to be
contrary to nature, we do not say that it came to be by chance, but by
spontaneity. Yet strictly this too is different from the spontaneous
proper; for the cause of the latter is external, that of the former
internal.
We have now explained what chance is and what spontaneity is, and in
what they differ from each other. Both belong to the mode of causation
'source of change', for either some natural or some intelligent agent
is always the cause; but in this sort of causation the number of
possible causes is infinite.
Spontaneity and chance are causes of effects which though they might
result from intelligence or nature, have in fact been caused by
something incidentally. Now since nothing which is incidental is prior
to what is per se, it is clear that no incidental cause can be prior
to a cause per se. Spontaneity and chance, therefore, are posterior to
intelligence and nature. Hence, however true it may be that the
heavens are due to spontaneity, it will still be true that
intelligence and nature will be prior causes of this All and of many
things in it besides.
Part 7
It is clear then that there are causes, and that the number of them is
what we have stated. The number is the same as that of the things
comprehended under the question 'why'. The 'why' is referred
ultimately either (1), in things which do not involve motion, e.g. in
mathematics, to the 'what' (to the definition of 'straight line' or
'commensurable', &c.), or (2) to what initiated a motion, e.g. 'why
did they go to war?-because there had been a raid'; or (3) we are
inquiring 'for the sake of what?'-'that they may rule'; or (4), in the
case of things that come into being, we are looking for the matter.
The causes, therefore, are these and so many in number.
Now, the causes being four, it is the business of the physicist to
know about them all, and if he refers his problems back to all of
them, he will assign the 'why' in the way proper to his science-the