The next element in the uncertainty which exists is as to how far the formula, either in the one case or the other, was conceived to involve the assent to any other propositions except those of the existence of the divine Persons or Person mentioned in the formula. Even this assent was implied rather than explicit. It is in the Apologists that the transition from the implicit was made. The teaching of Jesus Christ became to them important, especially in Justin Martyr.[676] The step by which it became explicit is of great importance, but we have no means of knowing when or how it was made.[677] It is conceivable that it was first made homiletically, in the course of exhortation to Christian duty.[678] When the intellectual contents of the formula did become explicit, the formula became a test. Concurrently with its use as a standard or test of belief, was probably the incorporation in it of so much of Christian teaching as referred to the facts of the life of Jesus Christ. But the facts were capable of different interpretations, and different propositions might be based upon them. In the first instance, speculation was free. Different facts had a different significance. The same facts of the life were interpreted in different ways. There was an agreement as to the main principle that the Christian societies were societies for the amendment of life. It is an almost ideal picture which the heathen Celsus draws of the Christians differing widely as to their speculations, and yet all agreeing to say, “The world is crucified to me, and I unto the world.”[679] The influence of Greek thought, partly by the allegorizing of history, partly by the construction of great superstructures of speculation upon slender bases, made the original standard too elastic to serve as the basis and bond of Christian society. When theories were added to fact, different theories were added. It is at this point that the fact became of special importance that the Gospel had been preached by certain persons, and that its content was the content of that preaching. It was not a philosophy which successive generations might modify. It went back to the definite teaching of a historical person. It was of importance to be sure what that teaching was. It was agreed to recognize apostolic teaching as the authoritative vehicle and interpretation of Christ’s. All parties appealed to it.[680] But there had been more than one apostle. The teaching was consequently that, not of one person, but of many.