ignores. What he says on this subject, therefore, is largely beside the mark.
At the same time, it must be admitted that, unless words, to some extent, had fixed meanings,
discourse would be impossible. Here again, however, it is easy to be too absolute. Words do
change their meanings; take, for example, the word "idea." It is only by a considerable process of
education that we learn to give to this word something like the meaning which Plato gave to it. It
is necessary that the changes in the meanings of words should be slower than the changes that the
words describe; but it is not necessary that there should be no changes in the meanings of words.
Perhaps this does not apply to the abstract words of logic and mathematics, but these words, as we
have seen, apply only to the form, not to the matter, of propositions. Here, again, we find that
logic and mathematics are peculiar. Plato, under the influence of the Pythagoreans, assimilated
other knowledge too much to mathematics. He shared this mistake with many of the greatest
philosophers, but it was a mistake none the less.
CHAPTER XIX Aristotle's MetaphysicsIN reading any important philosopher, but most of all in reading Aristotle, it is necessary to study
him in two ways: with reference to his predecessors, and with reference to his successors. In the
former aspect, Aristotle's merits are enormous; in the latter, his demerits are equally enormous.
For his demerits, however, his successors are more responsible than he is. He came at the end of
the creative period in Greek thought, and after his death it was two thousand years before the
world produced any philosopher who could be regarded as approximately his equal. Towards the
end of this long period his authority had become almost as unquestioned as that of the Church,
and in science, as well as in philosophy, had become a serious obstacle to progress. Ever since the
beginning of