  While relativism, particularly in the area of morality, is popularly seen as characteristic of sophists generally (see Bett 1989), in fact Protagoras is the only sophist to whom ancient sources ascribe relativistic views, and even in his case the evidence is ambiguous. A key text is the famous ‘Man the Measure’ sentence, the opening sentence of his work entitled ‘Truth’, which runs ‘Man is the measure of all things, of the things that are that they are and of the things that are not that they are not’ (Plato, Theaetetus 151e, Sextus Against the Mathematicians VII.60 (=DK 80B1)). In the Theaetetus (our principal source for this aspect of Protagoras’ teaching) this is interpreted as a claim of the relativity of the truth of all judgments to the experience or belief of the individual making the judgment, i.e., as subjectivism. On that interpretation, the way things seem to an individual is the way they are in fact for that individual. First illustrated by Socrates, who quotes this sentence, as a claim concerning sensory appearances, e.g., that if the wind feels cold to me and warm to you then it is cold for me and warm for you, in the course of the dialogue Socrates expands it to apply to all judgments, including itself, yielding the result that every belief is true for the person who holds it (and only for them), and hence that there is no objective truth on any matter. That this subjectivist interpretation was current in antiquity is shown by Aristotle’s attribution to Protagoras of the view that ‘it is equally possible to affirm and to deny anything of anything’ (Metaphysics 1007b20–22) and by Sextus’ evidence of Democritus’ critique of Protagoras mentioned above; Sextus reports Democritus (and Plato, see Theaetetus 170e–171c) as having argued that, given Protagoras’ thesis that every appearance (phantasia) is true, the thesis that it is not the case that every appearance is true, ‘which is itself in accordance with appearance (kata phantasian huphistamenon)’ is true; hence Protagoras’ thesis is self-refuting. But elsewhere in the Theaetetus (167c) Socrates explains Protagoras’ view by claiming on his behalf that ‘whatever things seem to each city to be fine and just are so for that city, so long as it maintains them (heōs an auta nomizēi)’: i.e., the truth about what is fine and just (which appears to indicate the truth of moral judgments generally) is relative not to the judgment of the individual, but to that of the society to which the individual belongs. If the wind feels cold to me, and I consequently believe that it is cold, there is no objective fact of the matter by reference to which that belief can be false; but if I believe that infanticide is wrong, whereas infanticide is sanctioned by the laws and customs of the state of which I am a citizen, then my belief is straightforwardly false, though of course it would come to be true if the state of which I am a citizen changed its laws and customs so as to condemn infanticide. Within a single Platonic dialogue, then, Protagoras is represented as maintaining both universal subjectivism and limited social relativism, though those two versions of relativism are mutually inconsistent. And there is a further twist. In the very passage of the Theaetetus where, according to Socrates, Protagoras maintains the social relativity of moral judgments (167b–c), he gives a pragmatic justification of the role of the expert, both in the individual and in the social context. In the individual case, while no appearance is truer than any other, some appearances are better than others, and it is the role of the expert (for instance, the doctor) to produce better appearances instead of worse (as those appearances are then judged even by the patient); while in the case of cities, some judgments of what is just etc. are better than others, and it is the role of the expert (in this case the expert orator) to persuade the city to adopt the better judgment. (He adds (167c7–d1) that the sophist improves those whom he educates in the same way, implying that not merely collective judgments but also individual judgments (about what?) may be better or worse.) This account of the role of the expert may imply that there are matters of fact of what is better and worse independent of the judgement of those whom the expert persuades. E.g., a city might initially judge it right to pursue its individual interest without any consideration of obligations to other cities, but then be persuaded that it was more in its long-term interest to respect treaties. That persuasion presupposes that the question of what is in the city’s long-term interest is a matter of fact, not merely a matter of how it now seems to the city.