At its very core Platonic philosophy is faced with a seemingly insurmountable difficulty: the transition from causes that are always of necessity immaterial to material effects. How can immaterial principles generate a material world? And, more importantly, why should they, given the Platonic predilection for the immaterial world? In his commentary on Plato’s Timaeus the Neoplatonist Proclus explains the existence of matter as the inevitable outcome of the completion of reality. For Proclus, the sensible world is the ultimate and necessary product of intelligible principles. During the sixteenth and seventeenth century the exact link between the material and immaterial world is a much debated issue, and discussions about the nature of matter occupy a central place. These debates are nearly always fuelled by the Timaeus, Plato’s most important work on cosmology, mediated by a long history of interpretation. The central aim of this project is to investigate the role of Proclus’ commentary in the reception of the Timaeus. A previous research project of ours has revealed the enormous influence of Proclus’ philosophy of mathematics in the elaboration of the mathematical worldview that underlies the birth of modern science. The role of Proclus’ natural philosophy as laid down in his commentary on the Timaeus may well be even more important, to the extent that early modern physics is heavily indebted to Proclus’ views on the relation between the material and the immaterial realm.