The relevance of Stoicism to later ancient philosophy can hardly be overstated. Stoic philosophy began in the wake of the creative explosion of philosophical activity initiated by Plato in the fourth century bce and sustained by Aristotle and the other followers of Plato. While the Academy entered its sceptical phase and Aristotle’s school invested its energy in scientific rather than philosophical inquiry, Zeno of Citium and his followers emerged as the principal philosophical heirs of Plato and Aristotle, held that position for at least two centuries, and continued to present a vital alternative to the revived Platonism and Aristotelianism of the early Roman Empire. The institutional cohesion of the Stoic school in the Hellenistic period was impressive, though it provided for a quite wide range of philosophical viewpoints; Stoicism avoided the unusual degree of intellectual conservativism and reverence for the founder which characterized Epicureanism in the period. In addition to the internal debates about doctrine which might be expected in any philosophical movement, from the later second century bce onwards Stoics came more often to differ among themselves on matters which we can suppose are connected with their attitude to Plato’s or Aristotle’s intellectual legacy.

One sign of this revival of interest was the intensity of debate, mostly in ethics, that seems to have followed from the joint embassy of philosophers sent by Athens to Rome in 155 bce. Carneades represented the Academy, Critolaus the Peripatos, and Diogenes the Stoic school. This grouping of the major schools is indicative of their importance in the intellectual life of a Mediterranean world that was already beginning to be shaped by the central role played by Rome; it foreshadows the importance of this trio of schools for debate in physics, metaphysics, ethics, and logic throughout the imperial period. It is certainly no accident that Carneades’ critique of both rival schools spurred them to revision and refinement of their doctrines.