Science, above all, teaches us to doubt—to question our conceptions of the world. It is an institutional embodiment of Freud's reality principle. It requires us to justify our beliefs about the world on empirical grounds. To provide such grounds, we pit our own hypothesis against a rival hypothesis and, when the data we obtain favor our own hypothesis over its rival, we consider what alternative explanations would account for our having obtained these data even if our own hypothesis were false.

Two kinds of deviation from the values and norms of science must especially concern social scientists. The scientistic deviation refuses to accept the demands of a thoroughgoing skepticism. Although this rebellion is disguised by an apparently zealous conformity to “science,” it is revealed when an investigator neglects the “clinical” or human demands of social science