  Of all the theories of desire considered here, learning-based theories of desire have the least a priori credibility: no one comes to grasp the idea of a desire through being taught about reward-based learning. A learning-based theory of desire is committed to holding that a desire can exist in a creature that cannot, by its nature, move or feel; so long as it can represent and learn in a certain way (and so long as these capacities are appropriately related), that suffices for a creature to have a desire. A priori, this is likely to seem outlandish. Our ideas about desire tell us that desires are all about actions and feelings, after all. The fact that the learning-based theory of desire holds that an organism could desire sunny days without feeling good about sunny days, without feeling bad about cloudy days, without being motivated to do whatever might help bring about a sunny day or even being moved to jump for joy when it turns sunny—this can be hard to swallow. The plausibility of learning-based theories thus requires either a rejection of a priori constraints on theories of desire, or acceptance of the idea that it is a priori that desires are best theorized as a natural kind that might, in principle, lack the features we most commonly associate with it (for versions of these criticisms, see, e.g., Bratman 1990; Brook 2006; Latham 2006).