If I feel it hot, it _is_ hot to me; if cold, then it _is_ cold: or if wine tastes sour, or bitter, because my digestion is in an abnormal state, then to me it _is_ sour or bitter; and it is no use to argue with me that it is not, but you must set right my disordered stomach, and then the wine will taste as it should. Apply this doctrine to the diversities of religious belief; the Christian says the Buddhist and the Mahommedan are wrong; and each of these retort the same on the Christian and on each other. A thing cannot be absolutely true _merely_ because this or that party asserts it, which is but a 'petitio principii.' Protagoras would have said, had he lived much later, and not altogether absurdly, 'If this form of religion is one that you embrace from conviction, and with entire faith in it, then to you it _is_ true.' And after saying this to the Christian, he would have turned to the Buddhist and the Mahommedan, and have repeated the same formula to each. Now Plato, to make the victory over Protagoras more complete, first shows, in the _Theætetus_, that he, Protagoras, by his doctrine of μέτρον ἄνθρωπος, virtually holds the same opinion as those (1) who make αἴσθησις the sole test of truth; (2) who, like Heraclitus, allow of no fixed existence, but hold that πάντα γίγνεται, states of things are always _coming into being_, because everything is in a state of perpetual flux. For it is evident that each of these views denies any permanent, stable, or objective existence of anything. Even a momentary perception is a fleeting sensation, not a true and real sense. While I say this paper is 'white,' _some_ discoloration of it occurred while the monosyllable was being pronounced, and therefore it was not true that the paper was _absolutely_ white. It appears to us that the question which Mr. Jowett moots as a difficulty in his Introduction (p. 326) is not really very important: 'Would Protagoras have identified his own thesis, "Man is the measure of all things," with the other, "All knowledge is sensible perception?" Secondly, would he have based the relativity of knowledge on the Heraclitean flux?' The latter, we think, Protagoras clearly does, when he says (p. 168, B.) ἵλεῳ τῇ διανοίᾳ ξυγκαθεὶς ὡς ἀληθῶς σκέψει, τί ποτε λέγομεν κινεῖσθαί τε ἀποφαινόμενοι τὰ πάντα τό τε δοκοῦν ἑκάστῳ τοῦτο καὶ εἶναι ἰδιώτῃ τε καὶ πόλει. To us it appears that Plato classed them together, simply because they are logically coherent and inseparable. He insists that all sensations imply a patient and an agent. Fire does not burn if there is nothing for it to consume. Colour is non-existent (being a mere effect of light), unless there is an eye to behold it. That indeed is true, and Epicurus and Lucretius also perceived (Lucr., ii. 795) that three conditions are wanted to produce colour--viz., light, an object to be seen, and an eye to see it. It is quite true, that a person sees a red or a blue cloth on a table while he looks at