The Theoretical Conflict between Rationalism and Empiricism, Mentalism and Naturalism, in Early Greek Philosophy Andrei V. Lebedev University of Crete (emeritus) Abstract This chapter falls into six parts, referred to below as “sections” I toVI. My starting point is the assumption that theories of knowledge do not emerge and do not exist in a conceptual void: they are usually integral parts of onto-epistemological complexes that we call philosophical systems. It is impossible to obtain a clear picture of what was going on in the early Greek epistemology without taking into account the contemporary dominant metaphysical paradigms and theories of being. Therefore, after a preliminary discussion of the (often neglected) problem of idealism (men- talism) in early Greek thought and criticism of what I call pseudo-historical developmentalism and misconceived category of ‘Presocratics’ in modern studies of pre-Platonic philosophy (section I), I will first delineate the gene- sis of two main conflicting metaphysical paradigms in their historical and socio-cultural contexts, those of the substance dualism (resp. mentalism) in sections II-III, on the one hand, and of the naturalistic monism in the section IV, on the other. Relying on the results of this investigation I will propose a general survey of the fundamental dispute between Greek rationalists and empiricists (resp. mentalists and naturalists) in section V, while the section VI will focus on the reflection of the conflict between two onto-epistemological complexes in the parable of ‘gigantomachia over being’ in Plato’s Sophist. 49