 Taking Kant’s method in the Prolegomena as his guide, Cohen claims that the method of Kantian philosophy is this. He thinks philosophy takes the theories of mathematical natural science as its starting point. It begins, as he puts it, with the “fact of mathematical natural science” (Cohen 1883, 119–120). Although Cohen does not emphasize it in the first edition of Kant’s Theory of Experience, he thinks (and it is consistent with his views) that this “fact of science” changes as science progresses. On the transcendental method, the philosopher takes the best physical theories of the day as her starting point, and thus the “fact of science” will be different for philosophers in different periods of the history of science.