216 orna harari
understanding the distinction made in this passage, Philoponus clearly
does not follow Aristotle here in assimilating defi nitions with explanations.
Th is conclusion fi nds further support in Philoponus’ comments on the
Posterior Analytics i .4.
In the Posterior Analytics i .4, Aristotle presents four senses in which
one thing is said to hold for another ‘in itself ’. Th e fi rst two senses are
predicative and they constitute Aristotle’s account for the predicative
relations that the premises of demonstration should express. According
to the fi rst sense, a predicate holds for a subject in itself if it is a part of
the defi nition of the subject. According to the second sense, a predicate
holds for a subject in itself if the subject is a part of the defi nition of the
predicate. Th e third sense distinguishes substances that exist in themselves
from attributes, which depend on substances, by virtue of their being
said of them. Th e fourth sense distinguishes a causal relation between
events from an incidental relation between events. In his comments on
this fourfold distinction Philoponus argues that only the fi rst two senses
of ‘in itself ’ contribute to the demonstrative method, 22 yet he also regards
the fourth sense (i.e. the causal sense) as relevant to the theory of demon-
stration. According to Philoponus, the causal sense of ‘in itself ’, though it
does not contribute to the formation of the premises of demonstration,
contributes to the ‘production of the whole syllogism’. 23 M o r e p r e c i s e l y ,
Philoponus argues that the causal sense of ‘in itself ’ expresses the rela-
tion between the cause, taken as the middle term of demonstration, and
the conclusion. Th e example Philoponus presents of this contention is
the following syllogism: Th e moon is screened by the earth. Th e screened
thing is eclipsed. Th erefore, the moon is eclipsed. Commenting on this
syllogism, Philoponus remarks that the fact that screening by the earth
is the cause of the eclipse of the moon is not expressed in the premises
of this demonstration, but its causal force becomes evident from its role
as a middle term. 24 In this discussion, then, Philoponus employs two dif-
ferent senses of ‘in itself ’ in accounting for the relations expressed in the
premises of demonstration and the relation between the middle term and
the conclusion. Th e premises of demonstration, according to Philoponus,
are ‘in itself ’ in one of the two fi rst senses delineated by Aristotle. Th at
is, their predicate is either a part of the defi nition of the subject or their
subject is a part of the defi nition of the predicate. By contrast, the middle22 65.10–11, Wallies.
23 65.15, Wallies.
24 65.16–19, 65.20–3, Wallies.