Chrysippus was the most prolific of all the Stoic philosophers. Sadly, only a few fragments of his over 700 works survive today. His philosophical style was to summarize the arguments of his opponents, usually quite fairly, and then provide his own position in a reply.

He was third to head the Stoa, after the founder, Zeno of Citium, and Cleanthes, both of whom were his teachers. He may also have studied with Arcesilaus, head of the (Platonic) Middle Academy. Chrysippus not only synthesized earlier Stoic thought into a philosophical system, but also integrated his great understanding of Hellenistic physics and formal logic, including propositional logic.

Many of the classical unsolved problems in philosophy are the direct result of thinking that they could be solved by logic, reason, and a deterministic physics. Although Chrysippus established deterministic physics, he challenged the idea that logical truths necessitated physical events (logical determinism).

He opposed the atomists and Epicurus' idea of irreducible chance in the universe. Stoic physics had no room for discrete entities like atoms. It was a continuum theory perhaps inspired by Parmenides, a plenum of material infinitesimals in contact everywhere, although he admitted an external void (κενόν) surrounding the cosmos (ὅλον κοσμος).

Chrysippus attempted to separate logical necessity from causal determinism and the idea of fate. He argued that all things were fated, including human decisions. But although the past was fixed and unchangeable, and all the antecedent events fated, future events were not necessitated. This gave him room for his subtle compatibility between free will and determinism, which he needed to establish moral responsibility.

Since future events were not necessary (though they are fated), human decisions are not constrained or forced by antecedent events or anything external to the mind. This lack of coercion, including one's heredity and environment, was critical for Chrysippus' idea that we have a freedom to assent (or not to assent) that made our decisions "depend on us." He called this πάρ’ ἡμᾶς or ἐξ ἡμῶν, depending on us, similar to Aristotle's ἐφ ἡμῖν.

This is the core idea of modern compatibilism. Chrysippus was the first compatibilist.

Notice that in Chrysippus' freedom our decisions are determined by our character and values, which were partially determined by factors beyond our control like heredity and environment. But they also include factors that we acquired freely in learning and training by our parents and educators.

Thus our character in not necessitated, though it is fated by the Stoic dogma of universal reason and common nature. Since the Stoics saw God as Nature, Chryssipus' idea of a fate compatible with freedom seems parallel to the religious idea of divine foreknowledge of our decisions that is compatible with our free will.

In this respect, Stoic determinism is less a physical determinism than a teleological or theological determinism. (See our dogmas of determinism.)

Chapter 6.6 - Language	Chapter 6.8 - Progress
Part Five - Problems	Part Seven - Afterword