Gut Reactions is an interdisciplinary defense of the claim that emotions are perceptions of changes in the body. This thesis, pioneered by William James and resuscitated by Antonio Damasio, has been widely criticized for failing to acknowledge that emotions are meaningful insofar as they represent concerns, not respiratory function and blood pressure. Fear represents danger, sadness represents loss. To explain this fact, many researchers conclude that emotions must involve judgments regarding one's relationship to the environment. Prinz offers a new unified account of the emotions that reconciles these two theories. He argues that emotions are embodied appraisals--they are perceptions of the body, but, through the body, they also allow us to literally perceive danger, loss, and other matters of concern.

The basic idea behind embodied appraisal theory is captured in the familiar notion of a "gut reaction," which has been overlooked by much emotion research. Using recent work in semantics, Prinz show how emotions can be meaningful without incorporating judgments or other cognitive states. Criticizing those who think that some emotions are social constructions, while others can be explained by evolutionary psychology, Prinz argues that all emotions are the same kind of phenomena, involving both nature and nurture.

Prinz also distinguishes emotions from other affective states, such as motivations and moods, and offers a theory of emotional valence (what makes some emotions good and others bad). Ultimately, his theory of emotion consciousness is inspired by recent research on the neural correlates of conscious vision. Drawing a parallel between emotion consciousness and visual consciousness, Prinz shows that emotion is a form of perception in the fullest sense. Where vision reveals the identity of objects in a given situation, emotion reveals how that situation bears on our well-being.