Hume’s potentially idealist approach to causation is clearly on view in his 1748 Enquiry concerning Human Knowledge, which was quickly translated into German and would eventually provide Kant with the stimulus for his own aprioristic rather than empiricist argument for idealism with regard not only to causation but to all of what he called the categories of pure reason, including especially substance and interaction as well as causation. But since Kant was not familiar with the contents of Hume’