This dissertation aims to investigate the ontology proposed by the character Socrates in the Platonic dialogues. In opposition tothe mostly accepted interpretation which attributes to the character Socrates the adoption of two distinct ontologies, I defend the hypothesis that the Socrates of the Platonic dialogues consistently argues from within a single ontological theory. This theory consists in the postulation of real and existing intelligible entities that act as the cause of the properties of sensible objects. The dissertation is divided in two parts. In the first part, I analyze the particularities of the Platonic composition as well as the construction of the actual reading paradigm of the Platonic works. In a second moment, I start investigating the first dialogues and claim that the ontological theory that underlies Socrates arguments in these works is the same as the one we can find in the middle dialogues. In the last chapter of the first part, I expose the Socratic arguments from the middle dialogues and I show how, in these woks, the underlying ontology of the first dialogues is more explicitly and informatively presented. The second part of the dissertation consists in an analysis of the critiques of the Theory of Forms that we find in the Parmenides dialogue. In the first moment of this second part, I argue that the Socrates from the Parmenides is again defending the same ontological theory from the middle and first dialogues. Afterwards, I show how the critiques constructed by the character Parmenides are valid and do present significant problems to the ontological theory of Socrates.