In this paper I focus on Proclus’ concept of the instrumental cause in his commentary on the Timaeus (In Tim.). Unlike earlier Neoplatonists who do not make much use of this type of causality, Proclus relates the instrumental cause to the hypostasis of nature (φύσις). The Demiurge uses nature as an instrument in his ordering and creation of the cosmos. How does Proclus arrive at this understanding of nature? I argue that the definition of nature as an instrumental cause is (...) in part based on his critical reception of Aristotle who identifies nature with the formal, efficient, and/or final cause. That is, Proclus did not develop his views on the causality of nature only by looking at the Timaeus (and other Platonic sources), but also by engaging with Aristotle’s rich – and, to a certain extent, authoritative – reflections on this issue. (shrink)