It was inevitable that it should be so. The growth of a confederation of Christian communities necessitated the definition of a basis of confederation. Such a definition, and the further necessity of guarding it, were inconsistent with that free utterance of the Spirit which had existed before the confederation began. Prophesying died when the Catholic Church was formed. In place of prophesying came preaching. And preaching is the result of the gradual combination of different elements. In the formation of a great institution it is inevitable that, as time goes on, different elements should tend to unite. To the original functions of a bishop, for example, were added by degrees the functions—which had originally been separate—of teacher.[194] In a similar way were fused together, on the one hand, teaching—that is, the tradition and exposition of the sacred books and of the received doctrine; and, on the other hand, exhortation—that is, the endeavour to raise men to a higher level of moral and spiritual life. Each of these was a function which, assuming a certain natural aptitude, could be learned by practice. Each of them was consequently a function which might be discharged by the permanent officers of the community, and discharged habitually at regular intervals without waiting for the fitful flashes of the prophetic fire. We consequently find that with the growth of organization there grew up also, not only a fusion of teaching and exhortation, but also the gradual restriction of the liberty of addressing the community to the official class. It was this fusion of teaching and exhortation that constituted the essence of the homily: its form came from the sophists. For it was natural that when addresses, whether expository or hortatory, came to prevail in the Christian communities, they should be affected by the similar addresses which filled a large place in contemporary Greek life. It was not only natural but inevitable that when men who had been trained in rhetorical methods came to make such addresses, they should follow the methods to which they were accustomed. It is probable that Origen is not only the earliest example whose writings have come down to us, but also one of the earliest who took into the Christian communities these methods of the schools. He lectured, as the contemporary teachers seem to have lectured, every day: his subject-matter was the text of the Scriptures, as that of the rhetoricians and sophists by his side was Homer or Chrysippus: his addresses, like those of the best professors, were carefully prepared: he was sixty years of age, we are told, before he preached an extempore sermon.[195]