This chapter compares two key figures in late nineteenth century debates concerning historical relativism: Wilhelm Windelband and Wilhelm Dilthey. Beneath the deep disagreements between these two authors, it reveals their common concern to immunize philosophy from the threat of historical relativism. The chapter traces how both philosophers sought to fend off relativism by defending the idea of an ahistorical and permanent stratum of philosophical thinking. It argues that although they succeeded in blocking historical versions of relativism, they did so at the cost of incurring a relativism vis-à-vis philosophical systems. This relativism turned out to be rooted not in the historicity of philosophy but in the timeless essence of philosophic...