This book is designed to be an intermediate-level text in the analysis of behavior that should all, in concept, somewhere between introductory texts, such as Keller and Schoenfeld's Principles of Psychology, Ferster & Perrott's Behavior Principles, or Whaley and Malott's Elementary Principles of Behavior; and more advanced works, such as Honig's Operant Behavior: Areas of Research and Application. However this textbook is self-contained and could, therefore, be read by the more diligent student without a background in behavioral analysis. Most of the issues discussed in this text are somewhat controversial, even among professional behavior analysts. So while we might hope to win a few minor controversies along the way, the primary purpose of this text is to increase the skill of the reader in using behavioral concepts in the analysis of complex behavioral phenomena. In addition, we do with selected topics in the philosophy of science in which the behavioral analysts will most likely be interested.