The Complete Aristotle (eng.)

is of the reasoned fact and demonstration not through the
cause is of the bare fact, one who knows it through the eclipse
knows the fact of the earth’s interposition but not the reasoned
fact. Moreover, that the eclipse is not the cause of the
interposition, but the interposition of the eclipse, is obvious
because the interposition is an element in the definition of
eclipse, which shows that the eclipse is known through the
interposition and not vice versa.
    On the other hand, can a single effect have more than one cause?
One might argue as follows: if the same attribute is predicable of
more than one thing as its primary subject, let B be a primary
subject in which A inheres, and C another primary subject of A, and
D and E primary subjects of B and C respectively. A will then
inhere in D and E, and B will be the cause of A’s inherence in D, C
of A’s inherence in E. The presence of the cause thus necessitates
that of the effect, but the presence of the effect necessitates the
presence not of all that may cause it but only of a cause which yet
need not be the whole cause. We may, however, suggest that if the
connexion to be proved is always universal and commensurate, not
only will the cause be a whole but also the effect will be
universal and commensurate. For instance, deciduous character will
belong exclusively to a subject which is a whole, and, if this
whole has species, universally and commensurately to those
species-i.e. either to all species of plant or to a single species.
So in these universal and commensurate connexions the ‘middle’ and
its effect must reciprocate, i.e. be convertible. Supposing, for
example, that the reason why trees are deciduous is the coagulation
of sap, then if a tree is deciduous, coagulation must be present,
and if coagulation is present-not in any subject but in a tree-then
that tree must be deciduous.
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    Can the cause of an identical effect be not identical in every
instance of the effect but different? Or is that impossible?
Perhaps it is impossible if the effect is demonstrated as essential
and not as inhering in virtue of a symptom or an accident-because
the middle is then the definition of the major term-though possible
if the demonstration is not essential. Now it is possible to
consider the effect and its subject as an accidental conjunction,
though such conjunctions would not be regarded as connexions
demanding scientific proof. But if they are accepted as such, the
middle will correspond to the extremes, and be equivocal if they
are equivocal, generically one if they are generically one. Take
the question why proportionals alternate. The cause when they are
lines, and when they are numbers, is both different and identical;
different in so far as lines are lines and not numbers, identical
as involving a given determinate increment. In all proportionals
this is so. Again, the cause of likeness between colour and colour
is other than that between figure and figure; for likeness here is
equivocal, meaning perhaps in the latter case equality of the
ratios of the sides and equality of the angles, in the case of
colours identity of the act of perceiving them, or something else
of the sort. Again, connexions requiring proof which are identical
by analogy middles also analogous.
    The truth is that cause, effect, and subject are reciprocally
predicable in the following way. If the species are taken
severally, the effect is wider than the subject (e.g. the
possession of external angles equal to four right angles is an
attribute wider than triangle or are), but it is coextensive with
the species taken collectively (in this instance with all figures
whose external angles are equal to four right angles). And the
middle likewise reciprocates, for the middle is a definition of the
major; which is incidentally the reason why all the sciences are
built up through definition.
    We may illustrate as follows. Deciduous is a universal attribute
of vine, and is at the same time of wider extent than vine; and of
fig, and is of wider extent than fig: but it is not wider than but
coextensive with the totality of the species. Then if you take the
middle which is proximate, it is a definition of deciduous. I say
that, because you will first reach a middle next the subject, and a
premiss asserting it of the whole subject, and after that a
middle-the coagulation of sap or something of the sort-proving the
connexion of the first middle with the major: but it is the
coagulation of sap at the