 Putnam is keen to emphasise the transcendental nature of his enterprise in this respect. He stresses that the kinds of constraints on reference that operate here and disprove the BIV hypothesis are not physical or merely analytic, but involve limitations on what is possible that can be arrived at through philosophical reflection on the nature of representation and meaning, and hence fit into a broadly Kantian model of how to respond to skepticism, albeit with more empirical elements: