Introduction
The challenge of Hellenistic philosophy, which is at the same time its
principal attraction, is the balance in it between continuity and change.
The accomplishments of the Pre-Socratic period of Greek thought and
the towering achievements of the fourth century (as seen in the work of
Plato and Aristotle) were never far from the concerns of the main Hellenis-
tic thinkers. Time after time we find inescapable evidence that Epicurus,
Zeno, and others worked on problems set by their predecessors, and
found their conceptual tools in the ideas of earlier philosophers. Yet the
novelty of the period is undeniable. After the eloquent explorations of
idealism by Plato and the exacting revision of his thought by Aristotle,
the Hellenistic thinkers struck out on a new path. The most efficient
way of outlining this balance between continuity and change is perhaps
to resort to that traditional crutch for the history of philosophy, -isms.
It is always dangerous to systemize philosophical ideas by grouping
them under general and therefore misleading headings. It tells us little
about the richness of Plato's thought, for example, to describe it as a
form of idealism; it is certainly no substitute for close study of the
living argument that makes his theory of Forms what it is. But such
generalizations do have a role to play in orienting the student to new
material. Taking our lead, then, from the systematic tendencies of the
Hellenistic period itself, let us suggest that three -isms best define the
continuity and novelty of the period: materialism, empiricism and natu-
ralism.
These headings correspond to the three divisions of philosophy that
became standard in the Hellenistic world, physics, logic and ethics. It
was the Academic Xenocrates who first claimed that this tripartite division
best described the structure of philosophy; the traditional grouping of
Aristotle's works into the Organon, Physical works, Metaphysics and
Ethical/Political philosophy (with practical subjects such as poetics and
rhetoric as a kind of appendix) owes as much to the systematic thrust of
his own work as it does to the tendencies of the Hellenistic Peripatetics
who organized the corpus as we now have it. The Stoics followed the
Xenocratean division exactly. The Epicureans eliminated logic in favour
of something they called 'canonic' (the study of sense-perception and
scientific method), which they subordinated to physics; but later tradition
forced their breakdown into the standard threefold division, as it did
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