This article analyzes the emerging notion of experimental method and its relationship to causality in the various editions of R. S. Woodworth's (1921, 1929, 1934, 1940; Woodward & Marquis, 1947) widely used introductory psychology textbook. Beginning with the 1934 edition, experiment was defined as manipulating an independent variable, while holding all other variables constant, and observing the effects on a dependent variable. By the 1940 edition, Woodworth implied that experiments of this type reveal causes, but other methods of inquiry do not. Woodworth's view of experiment and cause and his use of the terms independent and dependent variables appear to be the prototype for later textbooks. The context and implications of these changes are briefly discussed.