Autonomy of syntax

In linguistics, the autonomy of syntax is the assumption that syntax is arbitrary and self-contained with respect to meaning, semantics, pragmatics, discourse function, and other factors external to language. The autonomy of syntax is advocated by linguistic formalists, and in particular by generative linguistics, whose approaches have hence been called autonomist linguistics. 
The autonomy of syntax is at the center of the debates between formalist and functionalist linguistics, and for some scenarios it is contrasted with the principle of iconicity. The weaker version of the argument for the autonomy of syntax (or that for the autonomy of grammar), includes only for the principle of arbitrariness, while the stronger version includes the claim of self-containedness. The principle of arbitrariedness of syntax is actually accepted by most functionalist linguist, and the real dispute between functionalist and generativists is on the claim of self-containedness of grammar or syntax.
History.
The assumption of the autonomy of syntax can be traced back to the neglect of the study of semantics by american structuralists like Leonard Bloomfield and Zellig Harris in the 1940s, which was based on a neo-positivist anti-psychologist stance, according to which since it's presumably impossibile to study how the brain works, linguists should ignore all cognitive and psychological aspects of language and focus on the only objective data, that is how language appears in its exterior form. This paralleled the distinction between the two approaches in psychology, behaviorism, which was the dominant approach up until the 1940s, and cognitivism.
Over the decades, multiple instances have been found of cases in which syntactic structures are actually determined or influenced by semantic traits, and some formalists and generativists have reacted to that by shrinking those parts of semantics that they consider autonomous. Over the decades, in the changes that Noam Chomsky has made to his generative formulation, there has been a shift from a claim for the autonomy of syntax to one for the autonomy of grammar.