Aritsotle's hyle is contrasted with Plato's chora and Aquinas's prima materia. It is argued that Plato and Aristotle developed their concepts in response to very different needs, and that Aquinas's theory reflects a conflation of their views by Neoplatonic commentators. Hyle is shown to be an active potential to a determinate form in contrast to Aquinas's prima materia, which is a purely indeterminate passive potential. This gives a point of attachment in Aristotle's philosophy of nature for the later notion of (...) universal laws of nature. (shrink)