Although the development of systematic behavior modification techniques had impacted enormously on clinical theory and practice in the years leading up to 1978, when this book was first published, Edward Erwin addresses some of the remaining fundamental questions: what 'constitute' scientific principles of learning? Is behavior therapy really derived from them? How can ethical issues raised by the use of behavior modification techniques be resolved? His clear, readable analysis will be invaluable to anyone with a professional interest in behavior therapy, including graduate and advanced undergraduate students. Those philosophers of science whose focus is psychology will also find it a work of major importance that clarifies debates contemporary with the book's publication among psychologists, philosophers of science and legislators.