Many cultures have some version of the boogeyman, a mythical creature used by adults to keep children in line. "If you don't obey me and conform to our culture's expectations, bad things will happen to you." The bad things are personified by the boogeyman. Stray off the path of righteousness, and he'll get you.
Most parents and other adults are aware that there really isn't a boogeyman. I have to say "most" because I have become convinced after seeing the results of countless surveys that nothing is so far-fetched that approximately 30% of American adults won't believe it (e.g., angels, ghosts, Bigfoot creatures, ancient aliens, and all sorts of nonsense). Clearly, we can find people who will believe just about anything. But let's set all that aside for now. The adults could easily banish the boogeyman they have created if they wanted to, but they do not do so. Why? He's useful. He's there for a purpose, and he accomplishes it reasonably well.
Isn't Satan just another boogeyman? If the god in which many Christians claim to believe has the attributes most Christians assign to it, couldn't this god easily defeat Satan? We are told that Satan is an adversary of sorts, but that seems misleading. How could Satan possibly be anything more than a trivial adversary to such a powerful god? We are left with little choice but to conclude that the Christian god could easily end Satan but chooses not to. Perhaps Satan has some utility just like the boogeyman. Might that make Satan less of an adversary and more of an accomplice?
Many of the more moderate Christians do not like to talk about Satan or hell; however, many evangelical fundamentalist Christians certainly enjoy doing so. At least they seem to enjoy it up until the point where they must resort to mental gymnastics so as not to have to admit that they cannot answer the questions they are asked (e.g., why their god allows evil, why bad things inevitably happen to good people). This is where they fall back on "mysterious ways" or making vague references to some sort of hidden plan they think their god has for all of us.
Christian morality, at least the type of Christian morality one finds in many evangelical fundamentalist Christian circles today, is largely about guilt and fear. The Christian boogeyman is useful here. After all, salvation is not nearly as appealing unless what one needs to be saved from is sufficiently scary. That's where the Christian boogeyman comes in so handy.
Update: This post was revised in 2021 to improve clarity and correct some typos.
