The so-called cosmological argument (as it was fi rst labelled by Immanuel Kant) has played a central rôle within Aristotelian philosophy from the very beginning. In fact, we fi nd fi rst-cause arguments before Aristotle: most importantly, in Plato’s The Laws , Book X. The inference to the existence of a god or gods is central to Aristotle’s two most important works in metaphysics, Physics and Metaphysics . The Neo-Platonists (including Plotinus and Proclus), who saw themselves as building on Aristotle’s foundations, made this argument fundamental to their understanding of reality.