Locke: Simple and complex words/ideas

Locke is not very impressed by language. He finds it an imperfect medium through which we attempt to express our ideas, but often fail to do so. He is most satisfied with simple words which reflect simple ideas. These unambiguous words, like "sweet" and "bitter," will not cause controversy in conversation. Simple words, then, do not require definitions as their meanings are universally understood. Moreover, it would be impossible to apply an accurate definition to a simple word because the definition would consist of various synonyms, creating a complex description of something that has no composition at all.

Complex words, on the other hand, are subject to interpretation, like "modesty." People will have different opinions on the word, and they will entertain different ideas when the word is mentioned. Therefore, Locke insists upon having strict definitions for complex words, as this is the only way to sustain a concrete language. Still, Locke says that one must have experienced all of the simple ideas that make up the complex idea in order to fully understand the complex idea. He uses the example of a rainbow: a person born blind would not understand what a rainbow really is, even if it is described to him in exact detail.