Full Idea
The appreciation of the goodness of the effect is different from desire for the effect, and will originate not the desire but the sense of obligation to produce it.
Gist of Idea
Seeing the goodness of an effect creates the duty to produce it, not the desire
Source
H.A. Prichard (What is the Basis of Moral Obligation? [1925])
Book Reference
Prichard,H.A.: 'Moral Writings' [OUP 2002], p.1
A Reaction
A wonderful rebuttal of Hume, and a much better account of duty than Kant's idea that it arises from reason. Perception of value is what generates duty. And (with Frankfurt) we may say that love is what generates value.