All Sense-Perceptions Are True: Epicurean Responses to Skepticism and Relativism

Epicurean epistemology is infamous for the claim that all sense-perceptions are true. 1 This is how Lucretius puts it: what is perceived by any of the senses at any given time is true ( De Rerum Natura [ DRN ] 4.499). This claim—which I shall call SPT—seems deeply misguided. It appears obvious that sense-perception can err. The plan for this chapter is to show that SPT is a sophisticated philosophical proposal and, what is more, a proposal that aims to capture the truth in relativism. 2 SPT is presented in the midst of a series of anti-skeptical arguments. 3 And yet the skeptic is not the only opponent Lucretius has in mind. As I see it, much of the background for his position lies in Epicurean engagement with relativism. According to its best-known formulation in antiquity—in Plato’s Theaetetus —relativism embraces the view that all sense-perceptions are true. Epicurean epistemology, as I shall argue, aims to depart from relativism while preserving its insights. The most difficult question in interpreting SPT is how to understand ‘true.’ In which sense do Epicureans employ the predicate ‘true’ when they say that all sense-perceptions are true? Scholars currently tend to favor a propositional reading: ‘true’ is used in SPT as it is used when propositions are evaluated as true or false. They tend to reject an existential reading, according to which ‘true’ means something like ‘existent.’ By drawing on the comparison with relativism, I argue that both readings are misguided. SPT, I propose, is the claim that sense-perception is factive . Before I defend my reading (sections titled “Truth,” “Perception Is Factive,” and “The Theaetetus ”), an outline of Lucretius’s arguments is needed (sections titled “Lucretius’s Anti-Skeptical Arguments” and “The Criterial Argument and the Parity Argument”).