ABSTRACT: Aristotle repeatedly claims that rhetoric is, in its essential core, an ability to produce things he calls “pisteis”. The meaning of this claim depends on the meaning of this key term. But that meaning is disputed: some translate it as “means of persuasion”, others as something more like “proof”. The issue is whether these pisteis are things that in fact tend to persuade (“means of persuasion”) or things that should persuade (“proofs”). Here, I highlight how in ordinary Greek prior to the Rhetoric, Aristotle’s key term pistis has the latter, normative meaning (roughly: proper grounds for conviction) when it is used to refer to the basis on which someone is convinced (pisteuein). I briefly survey the use of these terms in Greek literature from Homer through to Epicurus and claim that over this time the meaning of these cognate terms does not change. Over this whole period, these were terms that were used in ordinary Greek to talk about the justification of states of credence and confidence. This explains why words like pistis and pisteuein are then picked up in the more technical treatments of human cognition and rationality, by philosophers. Everyone agrees that Aristotle saw rhetoric as an expertise in producing pisteis. This chapter’s conclusions suggest that what this means is that Aristotle saw rhetoric as an expertise in providing proofs, i.e. appropriate grounds for the orator’s listeners to be convinced of the speaker’s proposed conclusions. As such, these conclusions about the meaning of pistis lays important foundations for the larger project of showing that every major element of Aristotelian rhetoric was shaped by a conception of rhetoric as an expertise in providing listeners with justification for accepting the speaker’s proposed views. But they are also interesting in their own right, and have some suggestive implications for contested issues in the interpretation of Parmenides, and of the divided line in Plato’s Republic.