It is undoubtedly an hypothesis to account for a difficulty; but such too are the various explanations given by astronomers from Ptolemy to Newton of the apparent motions of the heavenly bodies, and it is as unphilosophical on that account to object to the one as to object to the other. Nor is it more reasonable to express surprise, that at this time of day a theory is necessary, granting for argument's sake that the theory is novel, than to have directed a similar wonder in disparagement of the theory of gravitation, or the Plutonian theory in geology. Doubtless, the theory of the Secret and the theory of doctrinal Developments are expedients, and so is the dictum of Vincentius; so is the art of grammar or the use of the quadrant; it is an expedient to enable us to solve what has now become a necessary and an anxious problem. For three hundred years the documents and the facts of Christianity have been exposed to a jealous scrutiny; works have been judged spurious which once were received without a question; facts have been discarded or modified which were once first principles in argument; new facts and new principles have been brought to light; philosophical views and polemical discussions of various tendencies have been maintained with more or less success. Not only has the relative situation of controversies and theologies altered, but infidelity itself is in a different,--I am obliged to say in a more hopeful position,--as regards Christianity. The facts of Revealed Religion, though in their substance unaltered, present a less compact and orderly front to the attacks of its enemies now than formerly, and allow of the introduction of new inquiries and theories concerning its sources and its rise. The state of things is not as it was, when an appeal lay to the supposed works of the Areopagite, or to the primitive Decretals, or to St. Dionysius's answers to Paul, or to the Cœna Domini of St. Cyprian. The assailants of dogmatic truth have got the start of its adherents of whatever Creed; philosophy is completing what criticism has begun; and apprehensions are not unreasonably excited lest we should have a new world to conquer before we have weapons for the warfare. Already infidelity has its views and conjectures, on which it arranges the facts of ecclesiastical history; and it is sure to consider the absence of any antagonist theory as an evidence of the reality of its own. That the hypothesis, here to be adopted, accounts not only for the Athanasian Creed, but for the Creed of Pope Pius, is no fault of those who adopt it. No one has power over the issues of his principles; we cannot manage our argument, and have as much of it as we please and no more. An argument is needed, unless Christianity is to abandon the province of argument; and those who find fault with the explanation here offered of its historical phenomena will find it their duty to provide one for themselves.