The bishop, with his presbyterate and diaconate, fitted to him as the strings to a harp, in the words of St. Ignatius, this was the instrument by which our Lord chose to take hold of the world. "Many nations of barbarians," St. Irenæus observes, "believing in Christ, follow the order of tradition without pen and paper, having salvation written in their hearts by the Spirit;"[71] but nowhere as to this point of episcopal regimen did this tradition vary. The Church having traversed the three centuries, assaulted from within by sects innumerable, and from without by a hostile Empire, emerges under this government alone. Nowhere was it without this settled order of the Episcopate. A presbyter not subject to a bishop, a single church or any number of churches not ruled by a bishop, these were unknown things. In the sects, indeed, there were all sorts of disorder and continued changes of government, just as there was incessant fluctuation of doctrine; the true and only Church showed itself precisely in this, that it preserved its doctrine and its government alike unchangeable. Eusebius observes how "the devices of opponents destroyed each other by their own violence. New heresies continually rose and fell, one giving way to the other, and corrupting themselves in a long series of the most diverse and strange conceptions. But the one Church, proceeding on the same lines, and in an even tenor, kept upon its path, ever increasing in brilliancy, and shedding forth upon every race of Greeks and barbarians the dignity, sincerity, and freedom, the tempered wisdom and purity, of the divine polity and philosophy;" where it is observable that by the words polity and philosophy he blends together the form of life and the truth of doctrine as coinherent with each other.[72]