Given limitations on our time, energy and interest, it is difficult to see how full rationality requires us to aim to fully develop literally all of our talents

By contrast with the maxim of the lying promise, we can easily conceive of adopting a maxim of refusing to develop any of our talents in a world in which that maxim is a universal law of nature. It would undoubtedly be a world more primitive than our own, but pursuing such a policy is still conceivable in it. However, it is not, Kant argues, possible to rationally will this maxim in such a world. The argument for why this is so, however, is not obvious, and some of Kant’s thinking seems hardly c