Abstract: The Pythagorean idea that number is the key to understanding reality inspired Neoplatonist philosophers in Late Antiquity to develop theories in physics and metaphysics based on mathematical models. This book examines this theme, describing first the Pythagorean interests of Platonists in the second and third centuries and then Iamblichus's programme to Pythagoreanize Platonism in the fourth century in his work On Pythagoreanism (whose unity of conception is shown and parts of which are reconstructed for the first time). The impact of Iamblichus's programme is examined as regards Hierocles of Alexandria and Syrianus and Proclus in Athens: their conceptions of the figure of Pythagoras and of mathematics and its relation to physics and metaphysics are examined and compared with those of Iamblichus. This provides insight into Iamblichus's contribution to the evolution of Neoplatonism, to the revival of interest in mathematics, and to the development of a philosophy of mathematics and a mathematizing physics and metaphysics.

Keywords: Iamblichus, Late Antiquity, mathematics, metaphysics, Neoplatonism, number, physics, Proclus, Pythagoras