Can desires be irrational? This paper focuses on the possibility that desires might be irrational because they fail to cohere with other mental states of the person in question. Recent literature on structural irrationality has largely neglected structural requirements on desire, and this paper begins to rectify that neglect. This paper endorses various rational requirements on desire, but primarily focuses on the instrumental requirement to desire the means to our ends. It explains how this requirement should be understood, and defends it from numerous objections, such as the worry that there are no real instrumental desires but only combinations of ultimate desires and beliefs, and the worry that it would require us to desire even very foolish means to our ends.
