Protestants believe, as a matter of unquestionable historical certainty, that at a very early period error and corruption — i.e., deviations from the scriptural standard in matters of doctrine, government, worship, and discipline — manifested themselves in the visible church gradually, but rapidly; that this corruption deepened and increased, till it issued at length in a grand apostasy — in a widely extended and well-digested system of heresy, idolatry, and tyranny, which involved in gross darkness nearly the whole of the visible church for almost a thousand years, until it was to some extent dispelled by the light of the Reformation. They believe that the soundness of this general view of the history of the church can be fully established by undoubted matters of fact, viewed in connection with the plain statements of Scripture (William Cunningham, Historical Theology, Vol. 1, 34-35).