From Gibbon's Volume 2: Christianity and the Civil Authority

Until Judge Posner's recent dissent in Elmbrook School District, I don't think I can remember the last time a judge cited to Gibbon's Decline and Fall of the Roman Empire (a quick Westlaw search shows only a handful of citations).  If evidence were needed that Judge Posner writes his own opinions, one could probably stop with that quotation.  I've got an old 1925 edition of the seven volumes edited by J.B. Bury which had been gathering dust here at home, and I started paging through it last night (a 12-volume on-line set may be found here).  The beginning of Volume 2 (Chapters 15 and 16) is all about the rise of Christianity and the early Christians' view of the existing Roman civil power.  Here's a bit from Chapter 15 where Gibbon's, one might say, ambivalent view of the early Christians shines through:

The Christians were not less averse to the business [of war] than to the pleasures of this world.  The defence of our persons and property they knew not how to reconcile with the patient doctrine which enjoined an unlimited forgiveness of past injuries and commanded them to invite the repetition of fresh insults.  Their simplicity was offended by the use of oaths, by the pomp of magistracy, and by the active contention of public life, nor could their humane ignorance be convinced that it was lawful on any occasion to shed the blood of our fellow-creatures, either by the sword of justice or by that of war; even though their criminal or hostile attempts should threaten the peace and safety of the whole community.*  It was acknowledged that, under a less perfect law, the powers of the Jewish constitution had been exercised, with the approbation of Heaven, by inspired prophets and by anointed kings.  The Christians felt and confessed that such institutions might be necessary for the present system of the world, and they cheerfully submitted to the authority of their Pagan governors.  But, while they inculcated the maxims of passive obedience, they refused to take any active part in the civil administration or the military defence of the empire.  Some indulgence might perhaps be allowed to those persons who, before their conversion, were already engaged in such violent and sanguinary occupations; but it was impossible that the Christians, without renouncing a more sacred duty, could assume the character of soldiers, of magistrates, or of princes.  

* The same patient principles have ben revived since the Reformation by the Socinians, the modern Anabaptists, and the Quakers . . . . [MOD note: see Philip Hamburger's piece about 6 years ago, Religious Freedom in Philadelphia, for parallel disagreements between the Revolutionaries and the Quakers on the question of conscientious objection to military service]