Nine leading scholars of ancient philosophy from Europe, the UK, and North America offer a systematic study of Book Beta of Aristotle's Metaphysics. The work takes the form of a series of aporiai or 'difficulties' which Aristotle presents as necessary points of engagement for those who wish to attain wisdom. The topics include causation, substance, constitution, properties, predicates, and generally the ontology of both the perishable and the imperishable world. Each contributor discusses one or two of these aporiai in sequence: the result is a discursive commentary on this seminal text of Western philosophy.