Linguistic determinism is the idea that language and its structures limit and determine human knowledge or thought, as well as thought processes such as categorization, memory, and perception. The term implies that people of different languages have different thought processes. Ludwig Wittgenstein expressed the idea Tractatus Logico-Philosophicus: "The limits of my language mean the limits of my world", "The subject does not belong to the world, but it is a limit of the world", and "About what one cannot speak, one must remain silent". This viewpoint forms part of the field of analytic philosophy. Though it played a considerable role historically, linguistic determinism is now discredited among mainstream linguists.