  One puzzle for most theories of desire strength is that desires seem to vary in their power to manifest the typical signs of strength even when it would seem that there is no variation in how much their ends are wanted. Think of a standard intrinsic desire: a desire for the welfare of a child. My disposition to act so as to benefit Cecilia might well be stronger when I am in a good mood than when I am feeling low, it might well be stronger when I am wide awake than when I am very sleepy, might well be stronger when the change in welfare will happen right now rather than in a month, and so on. These changes in disposition seem unlikely to mark changes in how much I desire Cecelia's welfare, however. Rather, they would seem to mark changes in how effectively my desire is poised to influence my actions. Similarly, the idea of certain harms to Cecelia's welfare will make me feel terrible (the idea of her being bitten by a dog, say) while others will make me feel less terrible (the idea of her getting chicken pox, say), even while my estimation of the harm to her welfare might make the two scenarios quite similar. Again, this would seem to indicate some idiosyncrasy in how effectively my desire is poised to influence my feelings, rather than indicating a difference in strength of desire (in this case, getting chicken pox seems like an expected ordeal of childhood, and that seems to blunt my felt response). And likewise for appearances of goodness and dispositions to pay attention.