Complex Ideas definable only when the simple ideas of which they consist have been got from experience.
Simple ideas, as has been shown, can only be got by experience from those objects which are proper to produce in us those perceptions.

When, by this means, we have our minds stored with them, and know the names for them, then we are in a condition to define, and by definition to understand, the names of complex ideas that are made up of them.

But when any term stands for a simple idea that a man has never yet had in his mind, it is impossible by any words to make known its meaning to him.

When any term stands for an idea a man is acquainted with, but is ignorant that that term is the sign of it, then another name of the same idea, which he has been accustomed to, may make him understand its meaning.

But in no case whatsoever is any name of any simple idea capable of a definition.
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