Cliometric metatheory: II. Criteria scientists use in theory appraisal and why it is rational to do so.

Definitive tests of theories are often impossible in the life sciences because auxiliary assumptions are problematic. In the appraisal of competing theories, history of science shows that scientists use various theory characteristics such as aspects of parsimony, the number, qualitative diversity, novelty, and numerical precision of facts derived, number of misderived facts, and reducibility relations to other accepted theories. Statistical arguments are offered to show why, given minimal assumptions about the world and the mind, many of these attributes are expectable correlates of verisimilitude. A statistical composite of these attributes could provide an actuarial basis for theory appraisal (cliometric metatheory).