Reason and good will

Reason and good will
When I was working the issue of good will, I found a good interesting thing which is about the relationship between reason and good will in Kant's work. In groundwork of metaphysics of morals, Kant refers to reason when he talk about the purpose of nature. According to his observation, if there is such called end of nature for human being as preservation of life, welfare if man, and in short, happiness of man, the natural instinct will be more efficient to carry out these purpose than reason. However, since the reason is given to us as practical faculty, the vocation of reason is to establish the good will which is absolutely good in itself and apart from any other purpose. To achieve this, reason only can fulfill the kind of itself, that the end is determined by reason itself. This is where the will come from.