The Evolution of God is full of footnotes and the literature cited in them is consistently the literature one would hope for: heavy on scholarly studies and light on popular treatments. In a climate in which discussions of religion, and especially of the intersection of religion and science, often seem superficial or rushed, Wright is to be commended for his close study. He is also to be commended for his refreshingly dispassionate tone. All this combines to provide an absorbing (and rant-free) tour of Western religion.
I second this: as a history of religion up to a certain historical point, the book is interesting, thought-provoking, helpfully structured, rich in information, and highly readable. If it pretended to be no more than that, I could stop here and simply recommend it highly.
However, there's a problem, or perhaps two or more problems. The author is not content to offer a (mostly) rant-free religious history from animism to Islam. He attempts to develop a theory as to how religion evolves, apparently he thinks inevitably, over time. More ambitiously still, he repeatedly suggests (though in a somewhat tentative, having-a-bet-each-way manner) that the narrative of religion's cultural evolution may be evidence for something divine behind it all.
As to the theory of history, I am not sure I ever totally grasped this. However, it is clear enough that ancient polytheistic civilizations were able to operate with different cities or city-states mutually recognising each other's gods. Polytheists do not necessarily limit the number of genuine gods at work in the world, and they are typically prepared to accept the reality of gods worshipped in other places. Often, gods with different origins come to be identified with each other -- same divinity, different name -- and sometimes entire pantheons are cobbled together from gods with disparate origins.
Polytheists' intrinsic tolerance of alien gods, and polytheism's strong historical tendency towards syncretism, become even more pronounced when multi-ethnic empires arise, such as the Babylonians, Persians, Greeks, and Romans. What this seems to reveal, however, is merely that polytheism has certain internal resources that make for a kind of religious tolerance, and that this was called upon historically by the economic integration of early states, through trade, and by the needs of large empires. It might be argued that civilizational integration and large-scale empire building more or less forced religion to be tolerant, and I have no doubt that there's some force in this. At the same time, it was the built-in logic of polytheism itself that made this possible in the first place. No deeper law or regularity seems to be responsible for that fact.
The next historical stage, after the formation of empires characterised by syncretism, is the development of monotheistic religions with universal aspirations and multi-ethnic appeal. This development contrasts with the idea, in early monolatrous and monotheistic systems, that the true god is the god for one people only. Again, however, monotheism seems to have its own internal logic: if there is only one true god, and if human beings from many racial or ethnic backgrounds are accepted as genuinely human (difficult to deny in a large multi-ethnic empire), it makes sense to extend access to the "true" god. It may not always work out in that way, since there are isolationist sects and cults even in modern times, and we cannot be sure what the tape of history would show if we replayed it. But still, it is at least not crazy to expect that some monotheistic cults would adopt universal pretensions, and that these might do well in the context of a multi-ethnic empire or a local "world" (such as that of the Mediterranean basin) intricately connected by trade and other contacts.
These are, however, rather modest, tentative, and local conclusions. Yes, socio-political circumstances may affect what kinds of religions do well, and the resources of some kinds of religion may be more advantageous than others in a particular socio-political setting. That seems hard to deny. In antiquity, this perhaps encouraged polytheistic syncretism and prodded monotheisms towards universalist pretensions. But even assuming that all this is correct, I see no reason to go further and postulate a more abstract law, such as that religion inevitably arises then evolves through a series of transactions that are mutually beneficial for those involved (such as the citizens of different states with different gods). That might sometimes happen, but sometimes it might not, and there certainly seems to be no reason to postulate a law that religions inevitably become more "moral" over time (in the sense of more willing to expand the circle of human beings who are regarded as moral equals).
It may even be that this expansion of the moral circle happens frequently as trade, improved travel and transport, empire-building, and so on produce a degree of cosmopolitanism. However, even that doesn't seem to be anything like a law of logic or nature -- it certainly did not prevent massacres, slavery, dispossession, and exercises in racial and cultural supremacy when European nations came into close contact with the very different peoples of Asia, sub-Saharan Africa, Australia, Oceania, and the Americas. Since the early centuries of Islam, where Wright stops, there has been plenty of religious intolerance. Even if a monotheism offers its god to everyone, it may be less tolerant of rival religions than the syncretic polytheism of antiquity. How, exactly, all this pans out in one situation or another may well depend on a blend of factors, perhaps including the degree of difference in military power between peoples that meet and interact. Perhaps, too, one factor is the perceived foreignness to each other of the peoples involved.
In all, I am totally unpersuaded that any kind of deep, abstract law applies to the development of religions. It is possible that attitudes and manners tend to be softened when (some) people gain a certain amount of leisure, and are free from the everyday struggle just to survive. Perhaps, too, as Hume thought, we do develop better understandings over time of what social arrangments are beneficial, so morality becomes less harsh. Those, however, are different points; they do not entail a logic or principle that drives the evolution of religion.
I am even less attracted to the thesis that the history of religion is evidence for some kind of divinity acting in time to lead humankind (or, I suppose, other intelligent creatures in the universe) to higher and higher levels of morality. If there are familiar social conditions that historically encouraged syncretism and/or universalist monotheisms, the explanation as to why that is so appears to be a material one all the way down. We can suggest why monotheists might (in some or many cases) want to claim that worship of their god is available to everyone, and why polytheism seems to have tolerant and syncretic tendencies. But there seems to be no deep mystery in any of this that needs a further -- supernatural or otherwise extraordinary -- explanation. Therefore, these facts do not stand as evidence for the existence of any sort of teleology or quasi-teleology, much less the existence of God, a god, or even a "god" (something that is godlike in a sense that needs to be specified, but not necessarily a being with intellect and personality).
And yet, Wright frequently pauses in his narrative to explore the possibility that the historical development of religion points beyond itself -- to something that could meaningfully be considered purposive or divine. Alas, it is never entirely clear what might count for the purpose. The orthodox Abrahamic deity would, presumably, but Wright hints that this unidentified "something" might be no more than an unexpected scientific principle or natural phenomenon.
In particular, he retells the well-known story of William Paley's attempt to prove the existence of God by referring to the functional intricacy of living things. Rather than drawing the moral that the appearance of design was an illusion -- faux design produced by millions of years of evolution -- Wright claims, surprise!, that there is a sense in which Paley was correct. It turns out, so Wright intimates, that there really is a "designer" of sorts, but that Paley misidentified it. Natural natural selection, a process unknown at the time, can produce the observed functional intricacy; therefore, natural selection was the unknown designer whose existence Paley insisted upon and sought to prove. We might think that evolution just is, but Wright wants to hold it out as a teleological process.
The suggestion here is that the "divine" or "purposive" "designer" that allegedly produces moral evolution in religions is not a personal god ... but just something unknown to us, something of great significance that stands in relation to us, who are ignorant of it, much as natural selection stood to Paley's contemporaries. What awaits our discovery, if so, may not be a divine revelation in the usual sense. It is not -- or not necessarily -- an onstage appearance from a supernatural person. Rather, it could be some dramatic breakthrough in intellectual understanding, analogous to what Darwin achieved in the nineteenth century.
This thought is confirmed in the final endnote to Chapter Eight, where Wright discusses the notion of purposiveness. He defines this so broadly as to include the functional adaptedness of lifeforms, the operation of natural selection itself, or the operation of some sort of larger scale natural selection (such as a cosmos-level process that might favour the origination of whole universes containing life and intelligence).
Unfortunately, the deep pattern of moral evolution that Wright seeks to explain, that he sees as pointing beyond itself, does not even seem to exist. There is no phenomenon crying out for a deeper explanation that involves purpose or design or divinity. Any tendency towards expansion of the moral circle can be explained in terms of more down-to-earth phenomena, such as the readily-understandable tendency for polytheists to tolerate each other's gods and rituals under certain circumstances. And even if something more did remain to be explained, it is simply confusing to use traditional religious language, suggesting that the explanation just might be the Abrahamic God -- you never know.
Why make a big deal of this while at the same time acknowledging that the unknown "something" might be purely material and impersonal? This kind of hedging, as if someone is looking over the author's shoulder, is the most frustrating aspect of what could be a very good book with all the wild metaphysics and quasi-theological speculation ripped out of it.
Despite all that, I recommend The Evolution of God for its scholarly synthesis of much that we know about religions' historical development, up to the early days of Islam. But be prepared: all the metaphysical huffing and riffing should be taken with a lot, as it were, of salt. Order in an entire pillar.