 A number of questions have been raised concerning Maritain’s epistemology, particularly concerning his characterization of philosophical knowledge. Moreover, while Maritain claims that there is a difference in method between the sciences and philosophy, some have argued that it is not clear what exactly that difference is (Vitoria 2011). For example, Maritain would follow Aquinas in holding that metaphysics uses demonstratio quia—demonstration from effects. But it would seem that science also sometimes uses such a method of demonstration. Thus, it is not clear what it is in the method (as distinct from the content of the premises) that differentiates a metaphysical proof (e.g., of God’s existence) from a scientific argument establishing the existence of a cause of a natural object.