For a convert from Greek and Roman paganism, Christianity would have presented many unfamiliar concepts, but none would have been stranger than that of the Christian Devil...Traditional pagan beliefs included no figure whose sole purpose was to create trouble and who could be regarded as the origin of all misfortune and evil. According to pagan ideas human malefactors were prompted by their own bad natures. Human misery could be influenced by divine powers, either for no perceptible reason or because they took offense at some behaviour. The gods and goddesses were often at variance with each other but none was solely concerned with upsetting unfortunate mortals. The Devil, whose origins lay in Jewish beliefs, provided a simpler and more satisfactory explanation for the suffering and injustice that the early Christians say around them.
Where to begin? Describing the Devil as a figure "whose sole purpose was to create trouble" and as someone who was "solely concerned with upsetting unfortunate mortals" makes the Devil sound like a mere trickster. That is certainly not how the Christians of the first century viewed him. For instance, one of the most prominent leaders in the early church, the Apostle Peter, spoke of how the Devil "prowls around like a roaring lion looking for someone to devour" (1 Peter 5:8, NIV), hardly the description of a mere troublemaker. Perhaps more important, the belief that Betts attributes to pagans-- that "human malefactors were prompted by their own bad natures"--is precisely the belief held by the original Christians! For example, another leading figure in the 1st century church, the Apostle James, spoke of how "each person is tempted when they are dragged away by their own evil desire and enticed. Then, after desire has conceived, it gives birth to sin..." (James 1:14, NIV--emphasis mine). Clearly, the early Christians certainly would not have agreed with claim that "the Devil made me do it," but would have insisted that we are all responsible for our own sins.
In short, while Betts may be an authority on the language of the original New Testament, he certainly is much less of an authority with regard to the beliefs of the earliest Christians--some of whom authored the New Testament. I suppose it could be said that this is yet another example of how being an expert in one field can all too easily mislead one into thinking that he or she is an authority in another field, even one that is closely related to his or her area of expertise. Perhaps we all need to learn a lesson from this!
Image of an early New Testament papyrus from Wikipedia