"[M]en talk to one another, and dispute in words, whose meaning is not agreed between them, out of a mistake that the significations of common words are certainly established, and the precise ideas they stand for perfectly known ; and that it is a shame to be ignorant of them. Both which suppositions are false ; no names of complex ideas having so settled determined significations, that they are constantly used for the same precise ideas. Nor is it a shame for a man not to have a certain knowledge of anything, but by the necessary ways of attaining it ; and so it is no discredit not to know what precise idea any sound stands for in another man’s mind, without he declare it to me by some other way than barely using that sound, there being no other way, without such a declaration, certainly to know it. Indeed the necessity of communication by language brings men to an agreement in the signification of common words, within some tolerable latitude, that may serve for ordinary conversation : and so a man cannot be supposed wholly ignorant of the ideas which are annexed to words by common use, in a language familiar to him. But common use being but a very uncertain rule, which reduces itself at last to the ideas of particular men, proves often but a very variable standard."
— John Locke, An Essay Concerning Human Understanding, Book III Chapter XI