 Third, even the so-called formal modes (5-2, 5–4, 5–5) might not be narrowly concerned with proof, but rather with everything that can lend credibility to something else. Consider Regress (5–2), the first of the formal modes. The text does not actually speak of proof (apodeixis) (this is obscured by Bury’s Loeb translation; 5–4 is the only place in Sextus’ report of the Five Modes that uses a cognate of apodeixis). Sextus’ language is wider: the mode deals with everything that can make something else credible. We might read this in the context of the Hellenistic view that proof is a species of sign (PH 2.122). A sign reveals something non-evident. Smoke that reveals fire has, from this point of view, a function and structure that is similar to a proof. The target of the Five Modes might be sign-inferences in general. If this is so, then their target might include what we would call inductive reasoning and causal explanations (when Sextus introduces a further set of modes, the Causal Modes, he says that they are not really needed, because the relevant work can be done by the Five Modes; PH 1.180–86). Taken together, the Five Modes deny all “proof, criterion, sign, cause, movement, learning, coming into being, and that there is anything by nature good or bad.” (DL 9.90). This is notably more than just proof. Indeed, it is an excellent summary of the key topics in Sextus’ discussions of logic, physics, and ethics.