logical necessities, as they say, those who assume a fifth element for the generation of the heavens and the stars in it, having rejected the opinions of their predecessors, needed an hypothesis of their own. But, another, strong in persuasive argumentation, rising in his turn against them, refuted and dissolved these theories and introduced his own personal opinion. If we undertake now to talk about these theories, we shall fall into the same idle chatter as they. But, let us allow them to refute