If all names were definable, it would be a Process IN INFINITUM.
I will not here trouble myself to prove that all terms are not definable, from that progress IN INFINITUM, which it will visibly lead us into, if we should allow that all names could be defined.

For, if the terms of one definition were still to be defined by another, where at last should we stop?
But I shall, from the nature of our ideas, and the signification of our words, show WHY SOME NAMES CAN, AND OTHERS CANNOT BE DEFINED; and WHICH THEY ARE.
6.

What a Definition is.
I think it is agreed, that a DEFINITION is nothing else but THE SHOWING THE MEANING OF ONE WORD BY SEVERAL OTHER NOT SYNONYMOUS TERMS.

The meaning of words being only the ideas they are made to stand for by him that uses them, the meaning of any term is then showed, or the word is defined, when, by other words, the idea it is made the sign of, and annexed to, in the mind of the speaker, is as it were represented, or set before the view of another; and thus its signification ascertained.
This is the only use and end of definitions; and therefore the only measure of what is, or is not a good definition.
7.

Simple Ideas, why undefinable.
This being premised, I say that the NAMES OF SIMPLE IDEAS, AND THOSE ONLY, ARE INCAPABLE OF BEING DEFINED.