In the chapters which follow, I will discuss various subjects from a theoretical-psychological perspective. Though the discussion will not be restricted to a single discipline, but ranges from experimental psychology to psychoanalysis, in each case the focus of attention is the scientific status of the theories scrutinized. Earlier versions of four of the chapters have been published elsewhere. Chapter 1, "Psychology and Philosophy of Science," is an expanded version of a Dutch paper written for Van Strien and Van Rappard's volume on the foundations of psychology, Grondvragen van de...