The essence of Freud's concept of the unconscious concerns psychological causality. Three critical causal principles are contained in Freud's theorizing: causal models are always—by the very nature of the mental apparatus—incomplete and partly false; psychoanalytic causal models are offered to gain knowledge and understanding, not prediction and control; there are different orders of causes which vary in efficacy and frame of reference. Preconditions are not causally relevant. Immediate experience usually presupposes an interior psychological causal process. It is, therefore, an epistemological error to explain all immediate experience by recourse to behaviorism or neurophysiology. The "pyramid of science," which assumes that all psychological causes are reducible to physical or sensorial causes, and that all hypothetical constructs must ultimately have sensory content, is the basis for oft-heard erroneous criticisms of the notion of unconscious causality.