putting himself, for the moment, in the place of Protagoras. As for dreams, the percepts are true
as percepts. As for the argument about pigs and baboons, this is dismissed as vulgar abuse. As
for the argument that, if each man is the measure of all things, one man is as wise as another,
Socrates suggests, on behalf of Protagoras, a very interesting answer, namely that, while one
judgement cannot be truer than another, it can be better, in the sense of having better
consequences. This suggests pragmatism. *
This answer, however, though Socrates has invented it, does not satisfy him. He urges, for
example, that when a doctor foretells the course of my illness, he actually knows more of my
future than I do. And when men differ as to what it is wise for the State to decree, the issue
shows that some men had a greater knowledge as to the future than others had. Thus we cannot
escape the conclusion that a wise man is a better measure of things than a fool.
All these are objections to the doctrine that each man is the measure of all things, and only
indirectly to the doctrine that "knowledge" means "perception," in so far as this doctrine leads
to the other. There is, however, a direct argument, namely that memory must be allowed as well
as perception. This is admitted, and to this extent the proposed definition is amended.
We come next to criticisms of the doctrine of Heraclitus. This is first pushed to extremes, in
accordance, we are told, with the practice of his disciples among the bright youths of Ephesus.
A thing may change in two ways, by locomotion, and by a change of quality, and the doctrine of
flux is held to state that everything is always changing in both respects. †And not only is
everything always undergoing some qualitative change, but everything is always changing all its
qualities--so, we are told, clever people think at Ephesus. This has
* It was presumably this passage that first suggested to F. C. S. Schiller his admiration of
Protagoras.â
€It seems that neither Plato nor the dynamic youths of Ephesus had noticed that locomotion
is impossible on the extreme Heraclitean doctrine. Motion demands that a given thing A
should be now here, now there; it must remain the same thing while it moves. In the
doctrine that Plato examines there is change of quality and change of place, but not change
of substance. In this respect, modern quantum physics goes further than the most extreme
disciples of Heraclitus went in Plato's time. Plato would have thought this fatal to science,
but it has not proved so.