"Pessimism" and its opposite, "optimism," are only secondarily philosophical theories or convictions; primarily they are personal opinions or attitudes, often widely prevalent, about the relative evil or goodness of the world or of men's experience of the world. As such they vary with the temperaments and value experiences of individuals, and with cultural situations far more than with philosophical traditions.

Both pessimism and optimism in the above sense may be reactions to experiences that vary in scope and content. Four types of reactions or judgments may be distinguished: (1) psychological or anthropological (involving judgments about the dominance of evil or good in one's own experience or in human experience generally); (2) physicalistic (judging the physical world to be dominantly evil or good); (3) historicistic (based on appraisals of the evil or goodness of a historical or cultural period or of the forces and institutions that determine history...