eby never have any idea of light,
or anything approaching it, though he understood never so well what
little globules were, and what striking on another body was. And
therefore the Cartesians very well distinguish between that light which
is the cause of that sensation in us, and the idea which is produced in
us by it, and is that which is properly light.

11. Simple Ideas, why undefinable, further explained.

Simple ideas, as has been shown, are only to be got by those impressions
objects themselves make on our minds, by the proper inlets appointed
to each sort. If they are not received this way, all the words in the
world, made use of to explain or define any of their names, will never
be able to produce in us the idea it stands for. For, words being
sounds, can produce in us no other simple ideas than of those very
sounds; nor excite any in us, but by that voluntary connexion which is
known to be between them and those simple ideas which common use has
made them the signs of. He that thinks otherwise, let him try if any
words can give him the taste of a pine apple, and make him have the true
idea of the relish of that celebrated delicious fruit. So far as he
is told it has a resemblance with any tastes whereof he has the ideas
already in his memory, imprinted there by sensible objects, not
strangers to his palate, so far may he approach that resemblance in his
mind. But this is not giving us that idea by a definition, but exciting
in us other simple ideas by their known names; which will be still
very different from the true taste of that fruit itself. In light and
colours, and all other simple ideas, it is the same thing: for the
signification of sounds is not natural, but only imposed and arbitrary.
And no DEFINITION of light or redness is more fitted or able to produce
either of those ideas in us, than the SOUND light or red, by itself.
For, to hope to produce an idea of light or colour by a sound, however
formed, is to expect that sounds should be visible, or colours audible;
and to make the ears do the office of all the other senses. Which is all
one as to say, that we might taste, smell, and see by the ears: a sort
of philosophy worthy only of Sancho Panza, who had the faculty to see
Dulcinea by hearsay. And therefore he that has not before received into
his mind, by the proper inlet, the simple idea which any word stands
for, can never come to know the signification of that word by any other
words or sounds