This lecture aims to show how the concepts of “meaning”, “universal” and “truth” reveal a unique property of human consciousness which is semantic consciousness. This property allows the subject to make a categorization that has the feature of generality, its results are susceptible to distinguishing between true and false, and may enter into logical relations of implication. Thanks to the analysis of these concepts, we discover different degrees of cognition. The issue of meaning is discussed in the so-called the theory of meaning. The dispute over universals stems from Aristotle’s polemic with Plato on the issue of ideas, and together they reveal the problem of truth.