Do desires provide reasons? An argument against the cognitivist strategy

According to the cognitivist strategy, the desire to bring about P provides reasons for intending to bring about P in a way analogous to how perceiving that P provides reasons for believing that P. However, while perceiving P provides reasons for believing P by representing P as true, desiring to bring about P provides reasons for intending to bring about P by representing P as good. This paper offers an argument against this view. My argument proceeds via an appeal to what I call the non-substitutability of perception, the thesis that, given that there is no independent evidence for P, one cannot substitute something that fails to provide reasons with respect to P for the perceptual experience that P, without altering the rational permissibility of believing that P. By contrast, I argue that it is always possible to substitute something that fails to provide reasons for a desire without altering the rational permissibility of an intention based on said desire. I take this to show that a desire does not provide reasons in a way analogous to perceptual experience.