John Philoponus (Greek : / f ɪ ˈ l ɒ p ə n ə s / ; Ἰωάννης ὁ Φιλόπονος ; c. 490 – c. 570), also known as John the Grammarian or John of Alexandria, was a Byzantine Greek philologist, Aristotelian commentator, Christian theologian and an author of a considerable number of philosophical treatises and theological works. He was born in Alexandria. A rigorous, sometimes polemical writer and an original thinker who was controversial in his own time, John Philoponus broke from the Aristotelian – Neoplatonic tradition, questioning methodology and eventually leading to empiricism in the natural sciences. He was one of the first to propose a " theory of impetus " similar to the modern concept of inertia over Aristotelian dynamics.