upon all
men, and was destroying the Sophistic teaching that the truth is
whatever each {145} individual chooses to think it is. We shall see
this more clearly if we reflect that a concept is the same thing as a
definition. If we wish to define any word, for example, the word man,
we must include in our definition only the qualities which all men
have in common. We cannot, for example, define man as a white-skinned
animal, because all men are not white-skinned. Similarly we cannot
include "English-speaking" in our definition, because, though some men
speak English, others do not. But we might include such a quality as
"two-legged," because "two-legged" is a quality common to all human
beings, except mere aberrations and distortions of the normal type.
Thus a definition is formed in the same way as a concept, namely, by
including the common qualities of a class of objects, and excluding
the qualities in which the members of the class differ. A definition,
in fact, is merely the expression of a concept in words. Now by the
process of fixing definitions we obtain objective standards of truth.
If, for example, we fix the definition of a triangle, then we can
compare any geometrical figure with it, and say whether it is a
triangle or not. It is no longer open to anyone to declare that
whatever he chooses to call a triangle is a triangle. Similarly, if we
fix upon a definition of the word man, we can then compare any object
with that definition, and say whether it is a man or not. Again, if we
can decide what the proper concept of virtue is, then the question
whether any particular act is virtuous can only be decided by
comparing that act with the concept, and seeing if they agree. The
Sophist can no longer say, "whatever seems to me right, is right for
me. Whatever I choose to do is virtuous for me." His act must be
judged, not by {146} his subjective impressions, but by the concept or
definition, which is thus an objective standard of truth, independent
of the individual. This, then, was the theory of knowledge propounded
by Socrates. Knowledge, he said, is not the same thing as the
sensations of the individual, which would mean that each individual
can name as the truth whatever he pleases. Knowledge means knowledge
of things as they objectively are, independently of the individual,
and such knowledge is knowledge of the concepts of things. Therefore
the philosophizing of Socrates consisted almost exclusively in trying
to