 Thus, Maritain writes, natural philosophy penetrates to the nature of its object. Metaphysics—which is also a kind of philosophic knowing—is concerned with purely intelligible being. Science, however, is at best ‘empiriological’—it does not lead us to being itself, but only to the observable and measurable. Consequently, to employ a method of scientific demonstration to establish or to criticize claims about the object of metaphysical knowledge is, to use Ryle’s classic term, a category mistake. It is precisely because he holds that empiricist and rationalist epistemologies do this, that Maritain takes issue with them.