The study of how language influences thought has a long history in a variety of fields. There are two bodies of thought forming around this debate. One body of thought stems from linguistics and is known as the Sapir–Whorf hypothesis. There is a strong and a weak version of the hypothesis which argue for more or less influence of language on thought. The strong version, linguistic determinism, argues that without language there is and can be no thought while the weak version, linguistic relativity, supports the idea that there are some influences from language on thought. And on the opposing side, there are 'language of thought' theories (LOTH) which believe that public language is inessential to private thought (though the possibility remains that private thought when infused with inessential language diverges in predilection, emphasis, tone, or subsequent recollection). LOTH theories address the debate of whether thought is possible without language which is related to the question of whether language evolved for thought. These ideas are difficult to study because it proves challenging to parse the effects of culture versus thought versus language in all academic fields. The main use of language is to transfer thoughts from one mind, to another mind. The bits of linguistic information that enter into one person's mind, from another, cause people to entertain a new thought with profound effects on his world knowledge, inferencing, and subsequent behavior. Language neither creates nor distorts conceptual life. Thought comes first, while language is an expression. There are certain limitations among language, and humans cannot express all that they think. Language of thought Language of thought theories rely on the belief that mental representation has linguistic structure. Thoughts are "sentences in the head", meaning they take place within a mental language. Two theories work in support of the language of thought theory. Causal syntactic theory of mental practices hypothesizes that mental processes are causal processes defined over the syntax of mental representations. Representational theory of mind hypothesizes that propositional attitudes are relations between subjects and mental representations. In tandem, these theories explain how the brain can produce rational thought and behavior. All three of these theories were inspired by the development of modern logical inference. They were also inspired by Alan Turing's work on causal processes that require formal procedures within physical machines. LOTH hinges on the belief that the mind works like a computer, always in computational processes.