 Talk of discovering what is unseen from what is evident calls to mind the maxim attributed to Anaxagoras (ca. 500–428 BCE): “Appearances are a vision of the invisible” (DK 59B21a; Graham 2010: 309). Not only was this principle employed in the Hippocratic writings, but it was said to have been endorsed by Democritus (ca. 460–371 BCE) (Sextus M VII 1.140). For all his scepticism regarding sense perception (DK 68B6–10; Graham 2010: 592–95), Democritus seemed to think it had an evidential role (Asmis 1984: 345). In particular, he apparently believed it could confirm the atomist theory which Leucippus (fl. ca. 450–420 BCE) had originated and he himself had embraced. There is, however, a difficulty here, as Democritus himself may have realized, for in one report he has the senses utter the following: “Wretched mind, after taking from us your evidence, do you overthrow us? Our fall will be your defeat!” (DK 68B125; Graham 2010: 597). The problem here is that while one can cite observable facts (such as the fact of motion) in support of atomism, that doctrine in turn suggests that appearances are deceptive (Barnes 1982: 559–64). As another fragment reads, “by convention color, by convention sweet, by convention bitter, but in reality atoms and void” (DK 68B9, 125; Graham 2010: 597). At first sight, anyway, the atomist doctrine seems self-defeating.