This elevation of doctrine due to causes internal to the Christian communities: but an external factor enters with case of Paul of Samosata: its results 345-347 Lines of reaction against this transformation: (1) Puritan or conservative tendency: Novatianism 347, 348 (2) Formation of esoteric class with higher moral ideal: Monachism 348, 349 Conclusion: The Greek spirit still lives in Christian Churches: the vital question is its relation to Christianity 349, 350 Two theories—permanence of the primitive, assimilative development: no logical third 350, 351 On either theory, the Greek element may largely go 351 The problem pressing: our study a necessary preliminary and truly conservative 352 New ground here broken: a pioneer’s forecast: the Christianity of the future 352, 353 LECTURE I. INTRODUCTORY. It is impossible for any one, whether he be a student of history or no, to fail to notice a difference of both form and content between the Sermon on the Mount and the Nicene Creed. The Sermon on the Mount is the promulgation of a new law of conduct; it assumes beliefs rather than formulates them; the theological conceptions which underlie it belong to the ethical rather than the speculative side of theology; metaphysics are wholly absent. The Nicene Creed is a statement partly of historical facts and partly of dogmatic inferences; the metaphysical terms which it contains would probably have been unintelligible to the first disciples; ethics have no place in it. The one belongs to a world of Syrian peasants, the other to a world of Greek philosophers. The contrast is patent. If any one thinks that it is sufficiently explained by saying that the one is a sermon and the other a creed, it must be pointed out in reply that the question why an ethical sermon stood in the forefront of the teaching of Jesus Christ, and a metaphysical creed in the forefront of the Christianity of the fourth century, is a problem which claims investigation. It claims investigation, but it has not yet been investigated. There have been inquiries, which in some cases have arrived at positive results, as to the causes of particular changes or developments in Christianity—the development, for example, of the doctrine of the Trinity, or of the theory of a Catholic Church. But the main question to which I invite your attention is antecedent to all such inquiries. It asks, not how did the Christian societies come to believe one proposition rather than another, but how did they come to the frame of mind which attached importance to either the one or the other, and made the assent to the one rather than the other a condition of membership.