In this important study D. M. Armstrong offers a comprehensive system of analytical metaphysics that synthesizes but also develops his thinking over the past twenty years. Armstrong's analysis, which acknowledges the "logical atomism" of Russell and Wittgenstein, makes facts (or states of affairs, as the author calls them) the fundamental constituents of the world, examining properties, relations, numbers, classes, possibility and necessity, dispositions, causes and laws. It will appeal to a wide readership in analytical philosophy.