Full Idea
A good will is that whereby alone [man's] being can have an absolute worth and in reference to which the being of the world can have a final purpose.
Gist of Idea
Only a good will can give man's being, and hence the world, a final purpose
Source
Immanuel Kant (Critique of Judgement II: Teleological [1790], C3 443), quoted by Christine M. Korsgaard - Aristotle and Kant on the Source of Value 8 'Kant'
Book Reference
Korsgaard,Christine M.: 'Creating the Kingdom of Ends' [CUP 1996], p.243
A Reaction
I wish Kant gave a better account of what a 'good' will consists of. This is an awful burden to bear when you are making decisions.