This is a post-Aristotelian Greek philosophical text, written at a crucial moment in the defeat of paganism by Christianity, AD 529, when the Emperor Justinian closed the pagan Neoplatonist school in Athens. Philoponus in Alexandria was a brilliant Christian philosopher, steeped in Neoplatanism, who turned the pagans' ideas against them. Here he attacks the most devout of the earlier Athenian pagan philosophers, Proclus, defending the distinctively Christian view that the universe had a beginning against Proclus' eighteen arguments to the contrary, which are discussed in eighteen chapters. Chapters 1-5 are translated in this volume.