We are told that Demokritus, as well as Plato and Aristotle, wrote against Protagoras. The treatise of Demokritus is lost: but we possess what the two latter said against the Protagorean formula. In my judgment both failed in refuting it. Each of them professed to lay down objective, infallible, criteria of truth and falsehood: Democritus on his side, and the other dogmatical philosophers, professed to do the same, each in his own way--and each in a different way.[79] Now the Protagorean formula neither allows nor disallows any one of these proposed objective criteria: but it enunciates the appeal to which all of them must be submitted--the subjective condition of satisfying the judgment of each hearer. Its protest is entered only when that condition is overleaped, and when the dogmatist enacts his canon of belief as imperative, peremptory, binding upon all (allgemeingültig) both assentient and dissentient. I am grateful to Aristotle for his efforts to lay down objective canons in the research of truth; but I claim the right of examining those canons for myself, and of judging whether that, which satisfied Aristotle, satisfies me also. The same right which I claim for myself, I am bound to allow to all others. The general expression of this compromise is, the Protagorean formula. No one demands more emphatically to be a measure for himself, even when all authority is opposed to him, than Sokrates in the Platonic Gorgias.[80] [Footnote 79: Plutarch, adv. Kolot. p. 1108. According to Demokritus all sensible perceptions were conventional, or varied according to circumstances, or according to the diversity of the percipient Subject; but there was an objective reality--minute, solid, invisible atoms, differing in figure, position, and movement, and vacuum along with them. Such reality was intelligible only by Reason. [Greek: No/mô| gluku/, no/mô| pikro/n, no/mô| thermo/n, no/mô| psuchro/n, no/mô| chroiê/; e)te/ê| de\ a)/toma kai\ keno/n. A(/per nomi/zetai me\n ei)=nai kai\ doxa/zetai ta\ ai)sthêta/, ou)k e)/sti de\ kata\ a)lêthei/an tau=ta; a)lla\ ta\ a)/toma mo/non kai\ ke/non.] Sextus Empiric. adv. Mathemat. vii. 135-139; Diog. Laert. ix. 72. See Mullach, Democriti Fragm. pp. 204-208. The discourse of Protagoras [Greek: Peri\ tou= o)/ntos], was read by Porphyry, who apparently cited from it a passage verbatim, which citation Eusebius unfortunately has not preserved (Eusebius, Præpar. Evang. x. 3, 17). One of the speakers in Porphyry's dialogue (describing a repast at the house of Longinus at Athens to celebrate Plato's birthday) accused Plato of having copied largely from the arguments of Protagoras--[Greek: pro\s tou\s e(\n to\ o)\n ei)sa/gontas]. Allusion is probably made to the Platonic dialogues Parmenides and Sophistes.] [Footnote 80: Plato, Gorgias, p. 472.] [Side-note: Plato's examination of the other doctrine--That knowledge is Sensible Perception. He adverts to sensible facts which are different with different Percipients.]