more abstract and narrow than Plato's ideas, of 'thing in itself,' to
which, if we reason strictly, no predicate can be applied.

The question which Plato has raised respecting the origin and nature of
ideas belongs to the infancy of philosophy; in modern times it would no
longer be asked. Their origin is only their history, so far as we know it;
there can be no other. We may trace them in language, in philosophy, in
mythology, in poetry, but we cannot argue a priori about them. We may
attempt to shake them off, but they are always returning, and in every
sphere of science and human action are tending to go beyond facts. They
are thought to be innate, because they have been familiar to us all our
lives, and we can no longer dismiss them from our mind. Many of them
express relations of terms to which nothing exactly or nothing at all in
rerum natura corresponds. We are not such free agents in the use of them
as we sometimes imagine. Fixed ideas have taken the most complete
possession of some thinkers who have been most determined to renounce them,
and have been vehemently affirmed when they could be least explained and
were incapable of proof. The world has often been led away by a word to
which no distinct meaning could be attached. Abstractions such as
'authority,' 'equality,' 'utility,' 'liberty,' 'pleasure,' 'experience,'
'consciousness,' 'chance,' 'substance,' 'matter,' 'atom,' and a heap of
other metaphysical and theological terms, are the source of quite as much
error and illusion and have as little relation to actual facts as the ideas
of Plato. Few students of theology or philosophy have sufficiently
reflected how quickly the bloom of a philosophy passes away; or how hard it
is for one age to understand the writings of another; or how nice a
judgment is required of those who are seeking to express the philosophy of
one age in the terms of another. The 'eternal truths' of which
metaphysicians speak have hardly ever lasted more than a generation. In
our own day schools or systems of philosophy which have once been famous