  these are the truths delivered by sense-impressions, preconceptions, and feelings (DL X 31), which would then be used to work out the truth of non-primitive propositions. The Stoics thought that the criteria of truth were special kinds of impressions, so-called ‘cognitive impressions’, which were of such a nature so as to guarantee their own truth (roughly speaking, they ‘come about from what is’ (DL VII 46) and are clear and distinct (see Frede 1983: 164)); they could also be used to work out the truth of other, unclear, matters. These two conceptions of the criterion, the Epicurean and the Stoic, were christened the ‘adelic’ and ‘prodelic’ conceptions by Brunschwig (1988: 230–233). (The terms ‘adelic’ and ‘prodelic’ derive from the Greek words adêlon and prodêlon, meaning ‘unclear’ and ‘clear’ respectively; thus, the ‘adelic’ conception of the criterion of truth is the one which emphasizes the role of the criterion in the discovery of unclear things, whereas the ‘prodelic’ conception is the one which emphasizes that those truths delivered by the criterion are clearly true.) Brunschwig shows in detail that Sextus conflates the two in his arguments against the criterion, although he acknowledges that this conflation does not dent the force of the objections that Sextus brings.