riable and uncertain,
as the variable opinion of each individual.

[Footnote 467: Maurice's "Ancient Philosophy," p. 114; Butler's
"Lectures on Ancient Philosophy," vol. ii. pp. 87, 88.]

The Sophists, who belonged to no particular school, laid hold on the
elements of skepticism contained in both the pre-Socratic schools of
philosophy, and they declared that "the sophia" was not only
unattainable, but that no relative degree of it was possible for the
human faculties.[468] Protagoras of Abdera accepted the doctrine of
Heraclitus, that thought is identical with sensation, and limited by it;
he therefore declared that there is no criterion of truth, and _Man is
the measure of all things_.[469] Sextus Empiricus gives the
psychological opinions of Protagoras with remarkable explicitness.
"Matter is in a perpetual flux, whilst it undergoes augmentations and
losses; the senses also are modified according to the age and
disposition of the body. He said, also, that the reason of all phenomena
resides in matter as substrata, so that matter, in itself, might be
whatever it appeared to each. But men have different perceptions at
different periods, according to the changes in the things perceived....
Man is, therefore, the criterion of that which exists; all that is
perceived by him exists; _that which is perceived by no man does not
exist_."[470] These conclusions were rigidly and fearlessly applied to
ethics and political science. If there is no Eternal Truth, there can be
no Immutable Right. The distinction of right and wrong is solely a
matter of human opinion and conventional usage.[471] "That which
_appears_ just and honorable to each city, is so for _that city_, so
long as the opinion prevails."[472]

[Footnote 468: Encyclopaedia Britannica, article "Sophist."]

[Footnote 469: Plato's "Theaetetus" (anthropos--"the individual is the
measure of all things"), vol. i. p. 381 (Bohn's edition).]

[Footnote 470: Lewes's "Biographical History of Philosophy," p. 117.]

[Footnote 471: "Gorgias," Sec. 85-89.]

[Footnote 472: Plato's "Theaetetus," Sec. 65-75.]

There were others who laid hold on the weapons which Zeno had prepared
to their hands. He had asserted that all the objects of sense were mere
phantoms--delusive and transitory. By the subtilties of dialectic
quibbling, he had attempted to prove that "change" meant "permanence,"
and "motion" meant "rest."[473] Words may, therefore, have the most
opposite and contradictor