It is often claimed that the debate between presentism and eternalism is merely verbal, because when we use tensed, detensed, or tenseless notions of existence, there is no difference in the accepted metaphysical statements between the adherents of both views. On the contrary, it is shown in this chapter that when we express their positions making use, in accordance with intentions of the presentists and the eternalists, of the tensed notion of existence (in the case of the presentists) and the detensed or tenseless notion (in the case of the eternalists), the controversy remains deep and very important for us, because both ontological claims express a different attitude to the existence of the flow of time. It is demonstrated that not only does the proposed approach to presentism and eternalism exactly express the intentions of the adherents of both views but it also offers a better understanding of them and explains at the same time the dynamism of the presentists’ ontology. The chapter takes for granted that we should assess metaphysical theories in a similar way as we assess scientific theories, that is on the basis of their explanatory value.