This article summarizes the main themes in the book What is Emotion? by Jerome Kagan (Yale University Press, 2007). The issues considered include: (1) the advantage of studying each phase of the cascade that begins with a brain reaction to an incentive and ends with an appraisal of a feeling state and/or a behavioral reaction; (2) distinguishing among appraisals with different origins; (3) replacing the current concern with consequences with more attention to the features of the brain and feeling states; (...) (4) a recognition of the weak relation between the language used to describe a feeling and both the underlying brain profile and a response; and (5) the reasons for variation in the feelings evoked by an incentive and for the appraisals of the feelings. (shrink)