The article compares views of Plato and Aristotle regarding their attitude to the problem of rationality. As a matter of fact, Plato and Aristotle take totally opposite stands on the question of the essence of philosophy, its subject and methods; they appeal to mutually incompatible interpretations of the very bases of being. For Plato, true being is spiritual, transcendent; it doesn’t fit in any rational-logical boundaries. For Aristotle, true being is corporeal and sensual; it is quite cognizable through rational-logical thinking. For Plato, the corporeal-sensual is an illusory “shade” of spirit; for Aristotle the very absolute spirit is a theoretical assumption, and this compulsory assumption, as a methodological admission, is necessary to substantiate the reality of the corporeal-sensual, “bodily” world. Aristotle most clearly formulated the idea of rational-logical totality which was very popular in ancient metaphysics and with which naturalistic philosophers, the Eleatics and the Sophists were mostly concordant. Whereas Plato “discovered” the transcensus and outlined the ways to the overrational and rather to the irrational-mystical comprehension of philosophical problems. In this sense, he constituted the opposition to the rational-logical tradition of ancient Greece as well as Orphics and Pythagoreans. Plato argued that the truth is the spiritual reality itself which is initially exposed to people: it is beyond contradictions and it embodies true being. He concludes from this that forms of being and forms of logical thinking are different. For Aristotle, on the contrary, the truth is the correspondence between forms of thinking and forms of being; it’s not the reality, but the reflection of the reality in structures of human consciousness. It is notable that this very treatment of the truth gained a foothold in West European philosophy and science. These two tendencies, aimed at the development of the rational and irrational models of the world, were elaborated further in the Christian tradition, continually “arising” in the form of discussions of the relation between faith and knowledge, of different ways of knowledge of God. © 2015 Mediterranean Center of Social and Educational Research. All rights reserved.