("Essay on
Human Understanding," Bk. III, chap. III, paragraph 6.) But it seems
that a word becomes general by being made the sign, not of an abstract
general idea, but of several particular ideas, any one of which it
indifferently suggests to the mind. For example, when it is said 'the
change of motion is proportional to the impressed force,' or that
'whatever has extension is divisible,' these propositions are to be
understood of motion and extension in general; and nevertheless it will
not follow that they suggest to my thoughts an idea of motion without
a body moved, or any determinate direction and velocity, or that I must
conceive an abstract general idea of extension, which is neither line,
surface, nor solid, neither great nor small, black, white, nor red,
nor of any other determinate colour. It is only implied that
whatever particular motion I consider, whether it be swift or slow,
perpendicular, horizontal, or oblique, or in whatever object, the axiom
concerning it holds equally true. As does the other of every particular
extension, it matters not whether line, surface, or solid, whether of
this or that magnitude or figure.

"By observing how ideas become general, we may the better judge how
words are made so. And here it is to be noted that I do not deny
absolutely there are general ideas, but only that there are any ABSTRACT
general ideas; for, in the passages we have quoted wherein there is
mention of general ideas, it is always supposed that they are formed by
abstraction, after the manner set forth in sections 8 and 9. Now, if
we will annex a meaning to our words, and speak only of what we can
conceive, I believe we shall acknowledge that an idea which, considered
in itself, is particular, becomes general by being made to represent
or stand for all other particular ideas of the same sort. To make this
plain by an example, suppose a geometrician is demonstrating the method
of cutting a line in two equal parts. He draws, for instance, a black
line of an inch in length: this, which in itself is a particular line,
is nevertheless with regard to its signification general, since, as it
is there used, it represents all particular lines whatsoever; so that
what is demonstrated of it is demonstrated of all lines, or, in other
words, of a line in general. And, as THAT PARTICULAR LINE becomes
general by being made a sign, so the NAME 'line,' which taken absolutely
is particular, by being a sign is made general. And