Posterior Analytics   

the teleological order the minor, C, must first take place, and the
end in view comes last in time.
The same thing may exist for an end and be necessitated as well. For
example, light shines through a lantern (1) because that which consists
of relatively small particles necessarily passes through pores larger
than those particles-assuming that light does issue by penetration-
and (2) for an end, namely to save us from stumbling. If then, a
thing can exist through two causes, can it come to be through two
causes-as for instance if thunder be a hiss and a roar necessarily
produced by the quenching of fire, and also designed, as the
Pythagoreans say, for a threat to terrify those that lie in Tartarus?
Indeed, there are very many such cases, mostly among the processes
and products of the natural world; for nature, in different senses
of the term 'nature', produces now for an end, now by necessity.
Necessity too is of two kinds. It may work in accordance with a
thing's natural tendency, or by constraint and in opposition to it;
as, for instance, by necessity a stone is borne both upwards and
downwards, but not by the same necessity.
Of the products of man's intelligence some are never due to chance
or necessity but always to an end, as for example a house or a statue;
others, such as health or safety, may result from chance as well.
It is mostly in cases where the issue is indeterminate (though
only where the production does not originate in chance, and the end is
consequently good), that a result is due to an end, and this is true
alike in nature or in art. By chance, on the other hand, nothing comes
to be for an end.
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The effect may be still coming to be, or its occurrence may be past
or future, yet the cause will be the same as when it is actually
existent-for it is the middle which is the cause-except that if the
effect actually exists the cause is actually existent, if it is coming
to be so is the cause, if its occurrence is past the cause is past, if
future the cause is future. For example, the moon was eclipsed because
the earth intervened, is becoming eclipsed because the earth is in
process of intervening, will be eclipsed because the earth will
intervene, is eclipsed because the earth intervenes.
To take a second example: assuming that the definition of ice is
solidified water, let C be water, A solidified, B the middle, which is
the cause, namely total failure of heat. Then B is attributed to C,
and A, solidification, to B: ice when B is occurring, has formed
when B has occurred, and will form when B shall occur.
This sort of cause, then, and its effect come to be simultaneously
when they are in process of becoming, and exist simultaneously when
they actually exist; and the same holds good when they are past and
when they are future. But what of cases where they are not
simultaneous? Can causes and effects different from one another
form, as they seem to us to form, a continuous succession, a past
effect resulting from a past cause different from itself, a future
effect from a future cause different from it, and an effect which is
coming-to-be from a cause different from and prior to it? Now on
this theory it is from the posterior event that we reason (and this
though these later events actually have their source of origin in
previous events--a fact which shows that also when the effect is
coming-to-be we still reason from the posterior event), and from the
event we cannot reason (we cannot argue that because an event A has
occurred, therefore an event B has occurred subsequently to A but
still in the past-and the same holds good if the occurrence is
future)-cannot reason because, be the time interval definite or
indefinite, it will never be possible to infer that because it is true
to say that A occurred, therefore it is true to say that B, the
subsequent event, occurred; for in the interval between the events,
though A has already occurred, the latter statement will be false. And
the same argument applies also to future events; i.e. one cannot infer