4. Names of simple ideas are undefinable.
Thirdly, The names of simple ideas are not capable of any definition;
the names of all complex ideas are. It has not, that I know, been yet observed by anybody what words are, and
what are not, capable of being defined; the want whereof is (as I am apt to think) not seldom the occasion of great
wrangling and obscurity in men's discourses, whilst some demand definitions of terms that cannot be defined; and
others think they ought not to rest satisfied in an explication made by a more general word, and its restriction, (or
to speak in terms of art, by a genus and difference), when, even after such definition, made according to rule,
those who hear it have often no more a clear conception of the meaning of the word than they had before. This at
least I think, that the showing what words are, and what are not, capable of definitions, and wherein consists a
good definition, is not wholly besides our present purpose; and perhaps will afford so much light to the nature of
these signs and our ideas, as to deserve a more particular consideration.
