Book excerpt: In Metaphysics 4 Aristotle discusses the nature of metaphysics, the basic laws of logic, the falsity of subjectivism and the different types of ambiguity. The full, clear commentary of Alexander of Aphrodisias on this important book is here translated into English by Arthur Madigan. Alexander goes through Aristotle's text practically line by line, attending to the logical sequence of the arguments, noting places where Aristotle's words will bear more than one interpretation and marking variant readings. He repeatedly cross-refers to the De Interpretatione, Analytics, Physics and other works of Aristotle, thus placing Metaphysics 4 in the content of Aristotle's philosophy as a whole.