[Sidenote: Progressive variation of human thought manifested by these councils.] [Sidenote: Pontifical power sustained by physical force.] Notwithstanding the contradictions and opposition they so frequently exhibit, there may be discerned in the decisions of these bodies the traces of an affiliation indicating the continuous progression of thought. Thus, of the four oecumenical councils that were concerned with the facts spoken of in the preceding pages, that of Nicea determined the Son to be of the same substance with the Father; that of Constantinople, that the Son and Holy Spirit are equal to the Father; that of Ephesus, that the two natures of Christ make but one person; and that of Chalcedon, that these natures remain two, notwithstanding their personal union. But that they failed of their object in constituting a criterion of truth is plainly demonstrated by such simple facts as that, in the fourth century alone, there were thirteen councils adverse to Arius, fifteen in his favour, and seventeen for the semi-Arians--in all, forty-five. From such a confusion, it was necessary that the councils themselves must be subordinate to a higher authority--a higher criterion, able to give to them or refuse to them authenticity. That the source of power, both for the council in the East and the papacy in the West, was altogether political, is proved by almost every transaction in which they were concerned. In the case of the papacy, this was well seen in the contest between Hilary the Bishop of Arles, and Leo, on which occasion an edict was issued by the Emperor Valentinian denouncing the contumacy of Hilary, and setting forth that "though the sentence of so great a pontiff as the Bishop of Rome did not need imperial confirmation, yet that it must now be understood by all bishops that the decrees of the apostolic see should henceforth be law, and that whoever refused to obey the citation of the Roman pontiff should be compelled to do so by the Moderator of the province." Herein we see the intrinsic nature of Papal power distinctly. It is allied with physical force. [Sidenote: The fall of Rome.] In the midst of these theological disputes occurred that great event which I have designated as marking the close of the age of Inquiry. It was the fall of Rome. [Sidenote: Spread of the barbarians.] [Sidenote: Capture and sack of Rome by Alaric.]