Abstract
<jats:title>Abstract</jats:title> <jats:p>This chapter reviews fundamental evolutionary, physiological, and neuropsychological concepts pertinent to understanding feelings within psychotherapy. It revisits historical positions such as the James-Lange theory and explores the idea of a conceptual nervous system, which includes the limbic system, arousal mechanisms, and the past triune brain model. The significance of these concepts for personality theory and the origins of behavior therapy are explained. Later individual difference models such as the behavioral inhibition system (BIS), behavioral activation system (BAS), and neuroticism are linked to more recent frameworks in affective neuroscience, with its focus on the core dimensions of activation and valence, and polyvagal theory with its evolutionary emphasis on feelings of safety. The chapter includes the more traditional significance of interoception and psychophysiological responses of the autonomic nervous system as measures of feelings and their relevance to clinical phenomena.</jats:p>