Last time we read Gregory Riley, he was arguing in One Jesus, Many Christs for the view that ancient Christian orthodoxy and heresy were on equal terms, and only the fact that orthodoxy won the battle keeps us from realizing it. It's still the same in this one: Riley is using Bauer and Koester (whose ideas we refute here, as does Glenn Miller here and here) when he needs to be using Dunn and Bauckham.
In a sense River of God is just a more polite and sophisticated version of what is offered by writers like Acharya S. The difference is that whereas she names names (Mithra, Dionysus, etc) Riley names ideas. Riley would have no quarter for a suggestion that Jesus was crucified because Mithra was crucified; instead it is more like, we are monotheists and believers in a devil and eschatology because the Zoroastrians or the Greeks were first: Christianity was not revealed, but evolved by taking ideas from the "river of God" (other religious streams) and adding, well, admittedly a dash of new ideas, but not much.
The problem with such a thesis is the same, though, as that of the Acharyas. The assumption is always, "A is like B, so A must be a copy of B." What about the major differences between A and B? "Oh, B evolved from A, you see." How about proof of derivation? Any port will do in a storm. For example, the Ebionites, a second-century Jewish-Christian group who denied the virgin birth and disliked Paul, called themselves "the poor". They must have existed in the first century -- Paul refers to them in Gal. 2:10 ("Only they would that we should remember the poor; the same which I also was forward to do."). It could not actually be "poor people" because it is "impossible to imagine that up to that time...Paul had forgotten to help poor people." [69]
Upon such slender threads are 150 years added to the history of a movement in order to give it equal time. The Greek word does mean "remember" but it also means to be mindful of, an admonition that fits in with the scenario that Paul here is working our particulars of aiding the Jerusalem church during famine -- that this cannot mean "remember" as Riley suggests is shown in the second phrase; how can Paul have been "forward to remember" in that way? It is far more likely that the later Ebionites took this epithet for themselves at a later date.
As a whole this book offers little more than the same disconnected meandering from idea to idea that we have seen in Riley's previous work. Proof on major points is no better. We may particularly highlight the matter of the Trinity, which we have elsewhere discussed and shown not to be, as Riley supposes, a late development (he is apparently unaware of all relevant intertestamental and Wisdom literature, other than Philo). In the end Riley admits that a standard Trinitarian view of the Father/Son relation can be found in John and Hebrews, but thinks it is nowhere else in the NT, and offers no treatment of the Wisdom sayings of Jesus and the Colossian and Phillipian hymns that show it is found amply attested in the rest of the NT as well.
Riley thinks that Satan was invented by the Persians; what about the book of Job which predates all of Zoroaster? He also thinks resurrection was gotten from there; apparently he forgot to consult Zoroastrian scholars, who do not all agree on this. Admirably, Riley does include some good material on the shame of the cross (see here) but never explains how Christianity got around this stumbling block, merely assuming that people bought into it wholesale.
The spirit of this book may be summed up with Riley's definition of heresy as "simply a perfectly workable and defensible viewpoint that did not get enough votes in the councils to carry the day." [227] Will Aztec sacrificial practices be defined with similar charity? In the world of Riley there is no right or wrong view (other than the view that one view is right and others are wrong), and as such, this book ignores the data for the sake of appeasing opposition.
-JPH