the most difficult in all of Aristotle's works and involve subtle refutations of the thought of Parmenides, Melissus and Anaxagoras.

In chapter 5, he continues his review of his predecessors, particularly how many first principles there are. Chapter 6 narrows down the number of principles to two or three. He presents his own account of the subject in chapter 7, where he first introduces the word matter (Greek: hyle) to designate fundamental essence (ousia). He defines