xvi Introduction
Aristotle's. The sceptics, both Academic and Pyrrhonian, did not, of
course, advance their own doctrines, so a division of philosophy does
not play a positive role in their work; but in criticizing nonsceptics, whom
they called 'dogmatists' (which means something like 'those who hold
definite beliefs'), they naturally followed the organizational scheme of
their opponents. The result, then, is that virtually all of Hellenistic
philosophy can be usefully broken down into logic (including epistemol-
ogy and the study of investigative method), physics (including what
Aristotelians called metaphysics), and ethics (a grouping broad enough
to include all of the so-called 'practical sciences', especially politics).
To return to the three -isms. The most evident general tendency in
Hellenistic physics is materialism, the rejection in one form or another
of the belief in incorporeal entities. This rejection is, of course, not
absolute; Epicureans maintained the existence of void; the Stoics found
that they needed four kinds of incorporeal entity: void, place, time and
'things said' or lekta^2 (singular lekton), a novel kind of incorporeal indis-
pensable for their philosophy of mind, their theory of language and their
analysis of causality. This proliferation of incorporeals might seem to
make 'materialism' a poor catch-phrase for orienting the student to Helle-
nistic physics and metaphysics, but that impression is misleading, if only
because the Stoics were always careful to stipulate that only corporeal
things exist, and that incorporeals, although they 'subsist', are not 'exis-
tent' things in the strict sense of the word.
Moreover, on the crucial issues both the Stoics and the Epicureans
set themselves deliberately and consciously against what they took to be
the views of Plato and Aristotle. The prime candidates for incorporeal
status in the fourth century were forms (in Plato's and perhaps in Aristot-
le's theory), Aristotle's Unmoved Mover(s), and the soul (or mind); it
is primarily because they reject the immateriality of these entities that
the Hellenistic schools earn the label 'materialists'.
Aristotle's commitment to 'dualism' is highly controversial; both au-
thors of the present work hold that there is a sense in which for Aristotle
the form of an individual thing and, therefore, soul too are incorporeal,
although not separately existing entities.^3 And no matter what one's view
of the character of soul in general, it is clear that in a human soul the
active intellect is incorporeal in the clearest sense. Moreover, the paradigm
instance of a substance for Aristotle was the Unmoved Mover, i.e., a
- Traditionally but misleadingly translated as 'meanings' or something similar. Long and
Sedley have recently coined the term 'sayable' for this difficult bit of Stoic jargon. - Some scholars doubt this; but for present purposes it need only be accepted that this
view of Aristotle as a kind of deviant Platonist was plausible in the Hellenistic period.