Physics   

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.
Part 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.)