This is the first complete translation into a modern language of the first part of the pagan Neoplatonist Simplicius of Cilicia's commentary on Aristotle's argument that the world neither came to be nor will perish. It is notable and unusual among the commentaries because Simplicius includes in his discussion lengthy representations of the Christian John Philoponus' criticisms of Aristotle along with his own, frequently heavily sarcastic, responses.