Crucially, rational wills that are negatively free must be autonomous, or so Kant argues. This is because the will is a kind of cause—willing causes action. Kant took from Hume the idea that causation implies universal regularities: if x causes y, then there is some universally valid law connecting Xs to Ys. So, if my will is the cause of my φing, then Φing is connected to the sort of willing I engage in by some universal law. But it can’t be a natural law, such as a psychological, physical, che