 During 17th-century debates between Catholics and Protestants, religion begins to refer to an abstract system of beliefs, especially when describing an oppositional structure.Through the Enlightenment this concept is further reified, so that by the nineteenth century G. W. F. Hegel defines religion as "Begriff", "a self-subsisting transcendent idea that unfolds itself in dynamic expression in the course of ever-changing history ... something real in itself, a great entity with which man has to reckon, a something that precedes all its historical manifestation".Smith concludes by arguing that the term religion has now acquired four distinct senses