This paper analyzes the ontology and epistemology of time in Lucretius’ De rerum natura. It uses the physiology of perception as well as epistemology to shed new light on the metaphysics. It presents an exegesis-based interpretation of the nature of time and of its perception, both arguing for and refining this interpretation by showing its explanatory power. The paper shows that Lucretius represents the perception of time or sensus temporis as a distinct sensory faculty, reconstructs how it emerges and operates, (...) and relates it to his account of perception more generally. The sense of time in turn is seen to explain aspects of related faculties, including thought and sight, and cases of apparent simultaneity. The paper thus contributes to, among other things, our understanding of the speed of perception and Lucretius’ account of the nature of time itself — arguing that Lucretius represents time as both continuous (not atomic) and real, as well as something perceived. (shrink)