In examining the dynamic, functional aspects of Piaget’s theory, one finds two major models for the understanding of interaction and change: assimilation/accommodation and scientific inquiry. However, neither of these models relates to the other, neither operates the way it is claimed to, and thus neither can do justice to the notion of active knowing. The positivism of Piaget’s peculiar brand of cybernetic bio-psychology precludes the understanding of either perception or action, with the result that his ‘interactionism’ fails to account for the crucial relationships between reason and experience, and judgment and behavior. At the same time, the functionalist epistemology implicit in the emphasis upon ‘adaptation’ undermines the possibility of true knowledge. This situation has not been rectified by the recent elaboration of a third model, that of ‘phenocopy’, or by the new model of equilibration.