We discuss a constructivist model of epistemic development based on the notion of increased complexity. This model proposes that as cognitive complexity increases by means of cycles of validation and invalidation, personal epistemic assumptions shift from positivism to constructivism, and preferred worldviews shift from mechanism to organicism—as defined by Pepper's (1942) taxonomy of world hypotheses. We report two studies in which we found, as predicted, a significant relationship among overall cognitive complexity, constructivist epistemic assumptions, and an organicist worldview. However, our attempt to discriminate the effects of the two theoretical dimensions of cognitive complexity (differentiation and integration) was not successful. Our data also indicate a dichotomy of ways of knowing: One is characterized by cognitive simplicity, objectvist epistemic assumptions, and a mechanistic/formistic worldview; the other is characterized by cognitive complexity, constructivist epistemic assumptions, and an organicist/contextualist worldview.