Philosophers have traditionally tried to understand the emotions and their bearing on rationality and moral motivation by assimilating emotion to other categories such as sensation, judgment, and desire. In recent years, moving away from the Cartesian identification of emotions with particular sensations, many philosophers have embraced "judgmentalism," the view that emotions are essentially evaluative judgments or beliefs, with only an accidental connection to the feelings and impulses we intuitively take as "emotional." Anger, for instance, either is or entails the belief that one has been wronged and that the source of injury or offense deserves punishment.

The book offers an evaluative theory of emotions that assigns emotion a role of its own in the justification of action. Greenspan analyzes emotions as states of object-directed affect with evaluative content possibly falling short of belief and held in mind by generalized comfort or discomfort.

She applies her analysis to "identificatory" emotions-- those based on evaluations from another person's standpoint, which she takes to be essential to moral motivation. In defense of their rational appropriateness, or justification by the agent's situation, Greenspan gives a general account of appropriate emotions allowing for cases of rational ambivalence.

The book describes the practical adaptiveness of emotions, or their motivational force as supplements to judgment, in terms of pressure to escape emotional discomfort. Ultimately, Greenspan claims that emotions are valuable in rational terms partly for their very resistance to rational control.