Halliday is always courteous and circumspect when referring to Chomsky: he only hints at their differences. Nevertheless, it becomes clear from the hints that their theories of language differ radically. Chomsky believes that language is innate: Halliday believes that it is learned. Chomsky believes that all human beings possess a grammatical programme hardwired into the brain: Halliday does not – he believes that grammar mirrors function and is mastered through experience. Chomsky believes in ‘Universal Grammar’: Halliday does not. Chomsky believes that language exists separately from experience: Halliday believes that language only develops through experience of other people and the world around us. Chomsky’s theory is Cartesian – in other words: mind exists separately from matter: Halliday’s ideas are Darwinian – in other words: language and the mind obey the same laws as all other aspects of reality. Chomsky’s theories are metaphysical: Halliday’s are scientific.From "Michael Halliday at 80: A tribute"
Building on what I mentioned earlier about Dan Everett -- Everett is lately touted as the first linguist to seriously challenge the foundations of Chomskian linguistics, and Halliday's work is extremely unsexy so it's rarely mentioned, but this paragraph shows that most of Everett's criticisms are implicit in Halliday's work. I've said before that I think SFL basically has a marketing problem: all the theory seems incredibly relevant, but then somebody tells you you're not allowed to call things nouns and verbs anymore and it's thanks but no thanks.
Side note: this paragraph also offers a fine example of the discourse I mentioned earlier, as well. Halliday = realistic linguistics = hard science = Darwin. Chomsky = 'theoretical' linguistics = metaphysics (which to a metaphysical naturalist = imaginary magic) = idle speculation = Descartes (who by the way gets an unnecessarily bad rap).
Not that I don't agree with the criticisms of Chomsky's way of explaining UG, but this description sets up a pretty unsustainable binary, if you ask me. And want an answer in fashionable jargon.
I'm blogging a lot so I must be thinking.