A hyper-emotion theory of psychological illnesses is presented. It postulates that these illnesses have an onset in which a cognitive evaluation initiates a sequence of unconscious transitions yielding a basic emotion. This emotion is appropriate for the situation but inappropriate in its intensity. Whenever it recurs, it leads individuals to a focus on the precipitating situation and to characteristic patterns of inference that can bolster the illness. Individuals with a propensity to psychological illness accordingly reason better than more robust individuals, but only on topics relevant to their illness. The theory is assessed in the light of previous research, a small epidemiological study of patients, and 3 empirical studies.