atter of fact man of affairs.
He was a plain, honest soldier. He had no great insight into any
philosophy, Socratic or otherwise. He was not attached to Socrates
primarily as a philosopher, but as an admirer of his character and
personality. If Plato puts the teaching of Socrates too high, Xenophon
puts it too low. But, in spite of this, Xenophon's Memorabilia
contains a mass of valuable information both about the life and the
philosophical ideas of Socrates.

The Socratic teaching is essentially ethical in character. In this
alone did Socrates bear any resemblance to the Sophists. It was the
Sophists who had introduced into Greek philosophy the problem of man,
and of the duties of man. And to these problems Socrates also turns
his exclusive attention. He brushes aside all questions as to the
origin of the world, or the nature of the ultimate reality, of which
we have heard so much in the philosophies of the earlier thinkers.
Socrates openly deprecated such speculations and considered all such
knowledge comparatively worthless as against ethical knowledge, the
knowledge of man. Mathematics, physics, and astronomy, he thought,
were not valuable forms of knowledge. He said that he never went for
walks outside the city, because there is nothing to be learnt from
fields and trees.

Nevertheless the ethical teaching of Socrates was founded upon a
theory of knowledge, which is quite simple, but extremely important.
The Sophists had founded knowledge upon perception, with the result
{143} that all objective standards of truth had been destroyed. It was
the work of Socrates to found knowledge upon reason, and thereby to
restore to truth its objectivity. Briefly, the theory of Socrates may
be summarized by saying that he taught that _all knowledge is knowledge
through concepts_. What is a concept? When we are directly conscious of
the presence of any particular thing, a man, a tree, a house, or a
star, such consciousness is called perception. When, shutting our
eyes, we frame a mental picture of such an object, such consciousness
is called an image or representation. Such mental images are, like
perceptions, always ideas of particular individual objects. But
besides these ideas of individual objects, whether through
sense-perception or imagination, we have also general ideas, that is
to say, not ideas of any particular thing, but ideas of whole classes
of things. If I say "Socrates is mortal," I am thinking of the
individual,