 In a work entitled On the Criterion or The Canon (Peri kritēriou ē kanōn), Epicurus is said to have argued that all sensations (aisthēseis) are reliable, there being nothing that can refute them (Diogenes Laërtius [DL] 10.31). Sextus sums up this Epicurean doctrine as the view that “all sensed things … are true and existent” (Sextus M VII 2.9). On the face of it, this seems an untenable position. Do our senses not deceive us? Do we not see sticks as bent where they enter water or a distant large object as small? There are two responses an Epicurean would make. The first is to make a clear distinction (comparable to that made by Aristotle  [sect. 3.2])  between our sensations and the opinions we form on the basis of what we sense. When it comes to our opinions, Epicurus held that “some them are true and others are false, since they are judgements of ours concerning what appears, and we judge sometimes rightly and sometimes wrongly” (Sextus M VII 1.210). When we make mistakes, in other words, it is not the senses that are to blame. Secondly, the senses are verdical because the impressions they form are not “purely private mental phenomena” (O’Keefe 2010: 100). They are brought about by the objects of which they testify, which emit a continuous flow of images or simulacra (eidōla) from their surfaces (Epicurus Ep. Hdt. 46–51). On this view, the senses are reliably informative, faithfully reflecting the objects that produced them, even if we later attribute to them a false propositional content.