This entry traces the life and ideas of Magda Arnold (1903–2002), a groundbreaking emotion theorist whose appraisal theory helped start the cognitive turn in emotion research. Arnold was born in Czechia, immigrated to Canada, and received her PhD from University of Toronto. She then immigrated to the United States, where she spent the rest of her career. Her mid-life conversion to Catholicism shaped both her career trajectory and her thought, as can be seen in her book The Human Person (published 1954). Her emotion theory, articulated in her book Emotion and Personality (published 1960), integrated Thomistic philosophy and modern research. She introduced the idea of appraisal, which made cognition an essential part of emotion. Arnold’s theory distinguishes between intuitive and reflective appraisals—a quick, often unconscious reaction and a more considered response. This connects to Arnold’s concept of the self-ideal, an overall life goal that organizes a person’s motivations and emotions.