The indispensability of the ‘postulate of practical reason with regard to Right’ to Kant's property argument in the Rechtslehre is now widely recognized. However, most commentators continue to focus their attention on the relation between the postulate and the deduction of the concept of intelligible possession. The nature of this relation remains a matter of dispute in part because the precise position of the postulate within chapter one of the Rechtslehre remains undecided. Given this, it is perhaps not surprising that (...) the related question has been neglected, as to why Kant should characterize the postulate of Right as a postulate of practical reason. Yet the fact that he does so is of some significance – especially if one recalls the definition in the Critique of Practical Reason of postulates of practical reason as practically necessary but theoretically indemonstrable propositions. What is of interest about this definition is not just the fact that it designates postulates as practically necessary and as theoretically indemonstrable at the same time – even more intriguing is the intimated relation between practical necessity and theoretical indemonstrability. Kant does not think the postulates' theoretical indemonstrability morally insignificant. To the contrary, their moral significance for us appears to be a function, in part, of their theoretical indemonstrability. (shrink)