Protagoras, Meno, Euthyphro,
Theaetetus, Gorgias, Republic; the nature of division is likewise
illustrated by examples in the Sophist and Statesman; a scheme of
categories is found in the Philebus; the true doctrine of contradiction
is taught, and the fallacy of arguing in a circle is exposed in the
Republic; the nature of synthesis and analysis is graphically described
in the Phaedrus; the nature of words is analysed in the Cratylus; the
form of the syllogism is indicated in the genealogical trees of the
Sophist and Statesman; a true doctrine of predication and an analysis of
the sentence are given in the Sophist; the different meanings of one
and being are worked out in the Parmenides. Here we have most of the
important elements of logic, not yet systematized or reduced to an art
or science, but scattered up and down as they would naturally occur in
ordinary discourse. They are of little or no use or significance to
us; but because we have grown out of the need of them we should not
therefore despise them. They are still interesting and instructive for
the light which they shed on the history of the human mind.

There are indeed many old fallacies which linger among us, and new
ones are constantly springing up. But they are not of the kind to which
ancient logic can be usefully applied. The weapons of common sense, not
the analytics of Aristotle, are needed for their overthrow. Nor is the
use of the Aristotelian logic any longer natural to us. We no longer put
arguments into the form of syllogisms like the schoolmen; the simple use
of language has been, happily, restored to us. Neither do we discuss the
nature of the proposition, nor extract hidden truths from the copula,
nor dispute any longer about nominalism and realism. We do not confuse
the form with the matter of knowledge, or invent laws of thought, or
imagine that any single science furnishes a principle of reasoning to
all the rest. Neither do we require categories or heads of argument to
be invented for our use. Those who have no knowledge of logic, like some
of our great physical philosophers, seem to be quite as good reasoners
as those who have. Most of the ancient puzzles have been settled on the
basis of usage and common sense; there is no need to reopen them. No
science should raise problems or invent forms of thought which add
nothing to knowledge and are of no use in assisting the acquisition of
it. This seems to be the natural limit of logic and meta