Sextus Empiricus adverts to the doctrines of Protagoras (mainly to point out how they are distinguished from those of the Sceptical school, to which he himself belongs) in Pyrrhon. Hypot. i. sects. 215-219; adv. Mathematicos, vii. s. 60-64-388-400. He too imputes to Protagoras both the two doctrines. 1. That man is the measure of all things: that what appears to each person is, _to him_: that all truth is thus relative. 2. That all phantasms, appearances, opinions, are _true_. Sextus reasons at some length (390 seq.) against this doctrine No. 2, and reasons very much as Protagoras himself would have reasoned, since he appeals to individual sentiment and movement of the individual mind ([Greek: ou)k ô(sau/tôs ga\r kinou/metha], 391-400). It appears to me perfectly certain that Protagoras advanced the general thesis of Relativity: we see this as well from Plato as from Sextus--[Greek: kai\ ou(/tôs ei)sa/gei to\ pro/s ti--tô=n pro/s ti ei)=nai tê\n a)lêthei/an] (Steinhart is of opinion that these words [Greek: tô=n pro/s ti ei)=nai tê\n a)lêthei/an] are an addition of Sextus himself, and do not describe the doctrine of Protagoras; an opinion from which I dissent, and which is contradicted by Plato himself: Steinhart, Einleitung, note 8). If Protagoras also advanced the doctrine--all opinions are true--this was not consistent with his cardinal principle of relativity. Either he himself did not take care always to enunciate the qualifications and limitations which his theory requires, and which in common parlance are omitted--Or his opponents left out the limitations which he annexed, and impugned the opinion as if it stood without any. This last supposition I think the most probable. The doctrine of Protagoras is correctly given by Sextus in the Pyrrhon. Hypot.] [Footnote 60: Aristotle, in commenting on the Protagorean formula, falls into a similar inaccuracy in slurring over the restrictive qualification annexed by Protagoras. Metaphysic. [Greek: G]. p. 1009, a. 6. Compare hereupon Bonitz's note upon the passage, p. 199 of his edition. This transition without warning, _à dicto secundum quid ad dictum simpliciter_, is among the artifices ascribed by Plato to the Sophists Euthydêmus and Dionysodôrus (Plat. Euthyd. p. 297 D).] [Footnote 61: The argument produced by Plato to discredit the Protagorean theory--that it puts the dog or the horse on a level with man--furnishes in reality a forcible illustration of the truth of the theory. Mr. James Harris, the learned Aristotelian of the last century, remarks, in his Dialogue on Happiness (Works, ed. 1772, pp. 143-168):-- "Every particular Species is, itself to itself, the Measure of all things in the Universe. As things vary in their relations to it, they vary also in their value. If their value be ever doubtful, it can noway be adjusted but by recurring with accuracy to the natural State of the Species, and to those several Relations which such a State of course creates."]