ABSTRACT
The Logical Positivist account of the a priori was not the only one in mid-twentieth century philosophy of science given that the neo-Kantians, pragmatists, and those influenced by them had alternatives. As a neo-Kantian, Cassirer can be seen as a transitional figure in the development of alternative theories of constitutive elements in science. The role of the pragmatic a priori in science is actually what is new and distinctive in his theory and the part that is a theory of constitutive elements in science. The laws of physics present the most interesting part of Lewis's pragmatic theory of the a priori. Poincare's argument about the conventionality of metric geometry, both an empirical determination and a traditional a priori determination of the principle have been ruled out. Lewis's pragmatic theory of the a priori is imbedded in a general theory of knowledge, or as he sometimes says, a theory of experience, which is set out in Mind and World Order.
