 There are also domains that are characterized in terms of subject matter or areas of inquiry. The Principle of Contradiction allows us to study mathematics, whereas the PSR allows us to study metaphysics, natural theology, and physics (G VII, 355–6; LC L2; AG 321). It is far from obvious that these two ways of assigning domains to the Principles are equivalent. For example, it would be natural to assume that metaphysics and natural theology would include necessary propositions and thus the PSR would encroach upon the territory assigned to the Principle of Contradiction according to the modal characterization.