I can’t juggle…so i’m not in the circus!

Why, according to Kant, is it immoral to neglect your natural gifts?  What are the assumptions that Kant makes about human nature to get this argument to work?  Are you convinced.

Kant feels that it is immoral to neglect your natural gifts, he puts it as out of self love we have a duty to cultivate our talents.  The major assumption that Kant makes about human nature to get this argument to work is that he assumes all men are rational.  A man is rational if he acts in what he thinks is in his own best interest.  Therefore to be rational as a man you should use your talents because it would be in your best interest if you have self love, which Kant assumes all men should have according to human nature.  To put this argument in the categorical imperative, determining your duty, Kant finds the maxim to be: If you don’t want to cultivate your talents, then do not.  Now for this to be a universal law in C.I. it must pass as a true law but according to human nature and Kant’s assumptions of self love and rationality this does not work out because we have a duty out of self love to cultivate our talents.  Although now a days are people as rational as Kant makes them out to be?  This surely is convincing if we believe that all men and women live by self love and are truly rational, but is this the case?