[Sidenote: Theology and religion, how related to each other.]
I have called natural theology a reasoned knowledge of a God or gods to distinguish it from that simple and comparatively, though I believe never absolutely, unreasoning faith in God which suffices for the practice of religion. For theology is at once more and less than religion: if on the one hand it includes a more complete acquaintance with the grounds of religious belief than is essential to religion, on the other hand it excludes the observance of those practical duties which are indispensable to any religion worthy of the name. In short, whereas theology is purely theoretical, religion is both theoretical and practical, though the theoretical part of it need not be so highly developed as in theology. But while the subject of the lectures is, strictly speaking, natural theology rather than natural religion, I think it would be not only difficult but undesirable to confine our attention to the purely theological or theoretical part of natural religion: in all religions, and not least in the undeveloped savage religions with which we shall deal, theory and practice fuse with and interact on each other too closely to be forcibly disjoined and handled apart. Hence throughout the lectures I shall not scruple to refer constantly to religious practice as well as to religious theory, without feeling that thereby I am transgressing the proper limits of my subject.