 According to the Marburg transcendental method  (section 2.1),  the “fact” of science is not static, but dynamic. In advocating this method, the Marburg Neo-Kantians are thus claiming that the principles that are a priori for science will evolve as theories change, and the concepts that function as categories will be radically reconceived as science progresses. There is then a new task, to identify the principles that are a priori in a given physical theory, and to investigate how the categories—space, time, substance, magnitude—are being reconceived in our current best physical theories. The Marburgers are thus committed to a view of scientific progress that emphasizes conceptual shifts in science. Scientists don’t just discover new facts: they also develop new concepts, and radically revise their fundamental concepts.