This document summarizes John Locke's ideational theory of meaning. According to Locke's theory, meaning is based on ideas in the mind that are formed through sense perception and experience, rather than innate ideas. Words signify these ideas, and ideas indirectly signify real-world objects. Locke believed language allows us to communicate our thoughts by representing them with words that stand for smaller components of thought called "Lockean ideas". However, some objections to Locke's theory are that ideas can vary between individuals whereas meaning is a public phenomenon, and that some meaningful sentences do not correspond to actual mental experiences.