Did Edward Gibbon blame Christianity for the decline of the Roman Empire?

I have now finally read Edward Gibbon's classic History of the Decline and Fall of the Roman Empire. Although certainly opinionated in a way that one might not consider up to the standards of historical research today, it is considered to be a ground-breaking work for its time (1776-1788) in the way that it used primary sources to tell its story.

But the most important reason I became interested in it is the pejorative way in which Gibbon is referred to in critiques of New Atheism. There is a general impression that Gibbon laid the blame for the collapse of the Roman Empire and the loss of its technology and learning at the feet of Christianity. In some circles, "Gibbonian fantasy" or "Gibbonian fiction" seems to be a short-hand for the belief that Christianity is singularly responsible for retarding scientific progress and causing the Dark Ages.

Having now read the book I have absolutely no idea where this is coming from. Maybe this idea is more clearly developed in some other work by the same author, but in the Decline and Fall I search for it in vain.

Don't get me wrong - it is clear that Gibbon had no love for Christianity. He argued in at least two sections of his book that early Christianity was more intolerant than the paganism that preceded it, and that Christianity wasted resources on piety that could have been better used for other, more practical purposes. (Nobody can seriously doubt the first claim, but the second seems a bit silly. Wasting resources on piety is not a Christian characteristic, it is a religious one; every pagan priest offering sacrifices to the gods and every Vestal Virgin performing a pointless ceremony could have more been more productively employed as an engineer, scholar, teacher, navigator, trader, or a variety of other professions.)

Due to his visible aversion to religion it is unsurprising that Christian apologists don't like Gibbon and want to cast aspersions on his work. But that does not mean that he actually made the argument that Christianity brought down the Roman empire and destroyed ancient learning. I really don't see where he did.

Even the Wikipedia page on the book as of today 20 June 2020 quotes a section that makes clear that despite Gibbon's dislike of Christianity he did not see it as a decisive factor: "if superstition had not afforded a decent retreat, the same vices would have tempted the unworthy Romans to desert, from baser motives, the standard of the republic" - in other words, the same decline would have taken place without Christianisation.

To any open-minded reader of his book it should become clear that his main culprit is an institutional process that can perhaps be usefully summarised as follows:

(1) As the republic expanded, the military was professionalised to increase its efficiency and flexibility of operation. What used to be a citizen army made up of free men expected to serve to defend the republic turned into an army of professional soldiers rewarded with property after a period of service.

(2) One of the consequences was that the average Roman citizen did not need, and ultimately did not want, to risk his life fighting to defend the republic. As the republic became an empire and grew even further, more and more of the armed forces were recruited from non-citizens, increasingly barbarian mercenaries or foederati, foreign tribes bribed to defend the empire from other, closely related tribes. It should be immediately obvious that these kinds of soldiers have considerably less loyalty to Rome than Roman citizen soldiers, and that mercenaries are only useful to you as long as you can guarantee their pay and nobody out-bids you. That alone could have been the empire's death knell, but...

(3) In addition, the empire had a severe institutional weakness in that there was never a clear rule of succession. There were phases where the next emperor was the previous emperor's son, whatever his ability, and others where the previous emperor would adopt a successor to ensure that the empire would be left in competent hands. But what if the emperor was a tyrant and got assassinated, with either no successor in place or his plan for succession as discredited as he was? Although technically an emperor needed to be recognised by the senate, imperator was a military title, and at any rate having control of a lot of swords is more of a, shall we say, practical argument than being endorsed by a bunch of elderly guys in togas. In practice the senate did not want those swords to be turned against themselves. It thus happened more and more that the next emperor was selected by the army and merely ratified by the senate. This again had two important consequences.

(4) First, the way for an ambitious officer to be elected emperor by the army was obviously to promise his fellow mercenaries a lot of money. In several parts of his book Gibbon is quite explicit about this tendency: the constant need to bribe the army to either get elected or to tolerate an emperor that the soldiers had not elected themselves drained the tax payers. Gibbon claims it also weakened the military vigour of the soldiers, who were at times living the good life spending their bribes while neglecting their training and insisting they shouldn't have to carry heavy armour.

(5) Second, frequently different parts of the army would elect different officers to be the new emperor. If both of them felt strong enough to give it a serious try, the empire would immediately be plunged into another short civil war. Just to decide whether the guy nominated by the Gaulish legions or the guy nominated by the Syrian legions gets to be the new ruler, they wasted the lives of thousands of soldiers who might more productively have been used to keep barbarian invaders or the Sassanian empire at bay.

So there we have it: the two key problems were the decreasing loyalty and increasing corruption of the armed forces and the institutional weakness of the republic. And both of them were probably entirely unavoidable. You cannot conquer and control an empire with an army made up of free farmers who have to travel back to northern Italy to bring in the harvest just when the enemy attacks in Mesopotamia, so you need a professional army. And even if you have very nice institutional arrangements they won't be of any use against a large army that has no loyalty to those institutions. The only alternative would have been not to have an empire in the first place.

I am not a historian. I do not know if this is accurate in all details. I do not know if this is really why the Roman empire declined, and I understand at least that plagues may have been another factor. The point is: this is Gibbon's argument, not that Christianity caused the decline.