pt. I. Theory building and theory appraisal. Construct validity in psychological tests ; High school yearbooks : a reply to Schwarz ; Nuisance variables and the ex post facto design ; Theoretical risks and tabular asterisks : Sir Karl, Sir Ronald, and the slow progress of soft psychology ; Appraising and amending theories : the strategy of Lakatosian defense and two principles that warrant it -- pt. II. Specific etiology. Specific etiology and other forms of strong influence : some quantitative meanings ; Specific genetic etiology, psychodynamics and therapeutic nihilism -- pt. III. Diagnosis and prediction. Antecedent probability and the efficiency of psychometric signs, patterns, or cutting scores ; Problem sets and solutions for Bayes theorem, base rates and prediction ; Wanted : a good cookbook ; When shall we use our heads instead of the formula? ; Some ruminations on the validation of clinical procedures ; Comparative efficiency of informal (subjective, impressionistic) and formal (mechanical, algorithmic) prediction procedures : the clinical-statistical controversy -- pt. IV. Taxometrics : coherent cut kinetics. Factors and taxa, traits and types, differences of degree and differences in kind ; Bootstraps taxometrics : solving the classification problem in psychopathology ; Clarifications about taxometric method -- pt V. Thinking clearly about psychology. Philosophy of science : help or hindrance? ; The power of quantitative thinking ; Why summaries of research on psychological theories are often uninterpretable.