The fundamental thesis from which the present study takes flight lies in a discussion of the philosophical function of the metaphorical word, which historically has been treated as having literal meaning and functions at the hands of the rationalist tradition. This paper will analyse both the traditional criticism of rhetoric —which has been thinking of it as a mere wrapper for the truth— as well as the defence of speculative power of metaphors which a particular branch of Renaissance Humanism undertakes. The paper will finally look at the ontological primacy of the metaphorical word. In this way, and taking as starting points some of the fundamental thesis of the philosopher Ernesto Grassi, we can reach a revaluation of rhetoric as a philosophical tool, which will allow us to legitimise the use of metaphor as a mechanism capable of expressing the changing nature of reality.