Speech and language pathologists, like all professionals who claim to be scientific in their practice, make a public commitment to operate on the basis of knowledge derived in accordance with sound scientific standards. Yet students in communication disorders are given relatively little grounding in the fundamentals of science; indeed, they often receive implicit encouragement to rely on clinical wisdom. This pathbreaking text introduces the principles of critical scientific thinking as they relate to assessing communication problems, deciding about alternative approaches to intervention, and evaluating outcomes. The author provides many illustrative examples to help readers contextualize the ideas. Her clear presentation will help not only undergraduate and graduate students but also established professionals reason more effectively about what they are doing and why. Though the examples come from speech and language pathology, this illuminating and readable book constitutes a valuable resource for all clinical practitioners.