I argue that Metaphysicsλ‎ is a unified work, and one which is not a continuation of the central books ΖΗΘ‎. It outlines an extensive project in First Philosophy, which has close connections with ΑΒΓΕ‎, but which proceeds on a different trajectory from ΖΗ‎. The principal problem in understanding λ‎ as a whole is how to reconcile Aristotle's explicit presentation of the book as a highly unified study with the disparate character of its two halves – the first a general‐metaphysical enquiry (...) into the features which changeable substances have as being substances of that kind, the second a detailed investigation of the specific character and activity of immaterial substances. My paper aims to show how this reconciliation is possible, and what we can learn about Aristotle's conception of first philosophy as a result. (shrink)