thinks, and there is the desk
which is thought. "I" am the subject of the thought, the desk is the
object of the thought. In general, the subject is that which thinks,
and the object is that which is thought. Subjective is that which
appertains to the subject, and objective is that which appertains to
the object. So the meaning of the distinction between subjective
impressions and the objective truth is clear. My personal impression
may be that the earth is flat, but the objective truth is that the
{115} earth is round. Travelling through a desert, I may be subject to
a mirage, and think that there is water in front of me. That is my
subjective impression. The objective truth is that there is nothing
but sand. The objective truth is something which has an existence of
its own, independent of me. It does not matter what I think, or what
you think, what I want, or what you want; the truth is what it is. We
must conform ourselves to the truth. Truth will not conform itself to
our personal inclinations, wishes, or impressions. The teaching of
Protagoras practically amounted to a denial of this. What it meant was
that there is no objective truth, no truth independent of the
individual subject. Whatever seems to the individual true is true for
that individual. Thus truth is identified with subjective sensations
and impressions.

To deny the distinction between objective truth and subjective
impression is the same as to deny the distinction between reason and
sense. To my senses the earth seems flat. It looks flat to the eye. It
is only through reason that I know the objective truth that the world
is round. Reason, therefore, is the only possible standard of
objective truth. If you deny the rational element its proper part, it
follows that you will be left a helpless prey to diverse personal
impressions. The impressions yielded by the senses differ in different
people. One man sees a thing in one way, another sees it in another.
If, therefore, what seems to me true is true for me, and what seems to
you true is true for you, and if our impressions differ, it will
follow that two contradictory propositions must both be true.
Protagoras clearly understood this, {116} and did not flinch from the
conclusion. He taught that all opinions are true, that error is
impossible, and that, whatever proposition is put forward, it is
always possible to oppose to it a contradictory proposition with
equally good arguments and with equal truth