 Insofar as Mendelssohn’s argument for religious tolerance has a religious premise, i.e., insofar as duties to others are founded upon the relation to God (“the more exalted sanction,” cited above), it is less advantageous, it has been argued, than Kant’s argument that rests simply on the innate right to freedom (Guyer 2018c). An analogous challenge from a Kantian perspective concerns the implications of Mendelssohn’s defense of speculation as a source of reason’s authority for his view of history. Mendelssohn’s rejection of the idea of moral progress in history and Kant’s endorsement of the idea coincide, it is argued (Sweet 2018), precisely with the contrast between Mendelssohn’s acceptance of an authority external to reason and Kant’s insistence upon a self-legislating reason.