Every managerial act rests on assumptions, generalizations, and hypotheses — that is to say, on theory. Our assumptions are frequently implicit, some… - Douglas McGregor

Man will exercise self-direction and self-control in the service of objectives to which he is committed.

Human behavior is predictable, but, as in physical science, accurate prediction hinges on the correctness of underlying theoretical assumptions. There is, in fact, no prediction without theory; all managerial decisions and actions rest on assumptions about behavior. If we adopt the posture of the ostrich with respect to our assumptions under the mistaken idea that we are thus “being ‘practical,” or that “management is an art,” our progress with respect to the human side of enterprise will indeed be slow. Only as we examine and test our theoretical assumptions can we hope to make them more adequate, to remove inconsistencies, and thus to improve our ability to predict.

Classical organization theory suffers from "ethnocentrism": It ignores the significance of the political, social, and economic milieu in shaping organizations and influencing managerial practice.