The proposed monistic interpretation of Parmenides’ ontology appears confirmed by the inescapable logic that permeates his whole thought. In spite of the fragmentary nature of his poem, it is possible to reconstruct the ironclad rationality of the Parmenidean ontology. This intrinsically coherent logic shows the absolute necessity of the monistic nature of being. From this perspective the absolute incompatibility between the perfect rationality and coherence of truth and the deceptiveness and inconsistency of doxa is made evident.