From our perspective, there are two especially important developments in the Hellenistic era. The first concerns the issue of ordinary concept formation. As we have seen, this subject had held little interest for either Plato or Aristotle, but with Epicurus and the Stoics things are very different. Epicurus showed a strong interest in explaining the formation of primary concepts – ‘prolepses’, as he called them – especially the prolepsis of the gods. As for the Stoics, we have already anticipated their interest in ordinary learning when we saw how they developed a stage-by-stage account of how we form concepts in the first seven years of life. That the Hellenistic philosophers were interested in ordinary learning is uncontroversial and not something that needs to be laboured; it can instead be allowed it to speak for itself over the next two chapters. But when set against the Platonic and Aristotelian indifference to the subject, it gives rise to a new question: why was it the Hellenistic period in which the issue was placed on the agenda for the first time? We shall turn to this question on pp. 217–18 below after we have examined the Hellenistic theories in more detail.

The other thing that happened in the Hellenistic era was the emergence of a new theory of innateness. The burden of section I was that Plato's theory of recollection is not be be seen as a theory of ‘innate ideas’ in the seventeenth-century sense, a theory in which nature, or God, has endowed us at birth with concepts that help to form ‘the inner core and mortar of our thoughts’, as Leibniz was to put it.