Some Externalists and Emergentists actually reject the idea that the human capacity for language yields “a potentially infinite array of expressions”. It is often pointed out by empirically inclined computational linguists that in practice there will only ever be a finite number of sentences to be dealt with (though the people saying this may underestimate the sheer vastness of the finite set involved). And naturally, for those who do not believe there are generative grammars in speakers’ heads