Building on work of Dieter Henrich, the essay argues that Kant's legal metaphors suggest that the Deductions in Kant's first two Critiques share a common structure. Each has a first part corresponding to the "factum" of a legal deduction, and a second part corresponding to a proof of the validity of a legal claim from this basis. The relevant factum in the first Critique is the fact--revealed by the Metaphysical Deduction--that the categories have a priori origins; in the second, it is the so-called 'Fact of Reason'. Each 'factum' both requires a proof and admits of one.