C.S. Lewis found the "moral law" argument quite convincing, and it was a big factor in his conversion from atheism to Christianity. I read his book Mere Christianity a few years ago, which devotes a few chapters to this topic. While most of it didn't seem like strong evidence for God's existence to me, there's part of it that I find myself pondering once in a while. I looked up that part, and here it is, from the chapter called "The Invasion:"
If Dualism [the idea that there are two higher powers, one good and one bad] is true, then the bad Power must be a being who likes badness for its own sake. But in reality we have no experience of anyone liking badness just because it is bad. The nearest we can get to it is in cruelty. But in real life people are cruel for one of two reasons— either because they are sadists, that is, because they have a sexual perversion which makes cruelty a cause of sensual pleasure to them, or else for the sake of something they are going to get out of it—money, or power, or safety. But pleasure, money, power, and safety are all, as far as they go, good things. The badness consists in pursuing them by the wrong method, or in the wrong way, or too much. I do not mean, of course, that the people who do this are not desperately wicked. I do mean that wickedness, when you examine it, turns out to be the pursuit of some good in the wrong way.
You can be good for the mere sake of goodness: you cannot be bad for the mere sake of badness. You can do a kind action when you are not feeling kind and when it gives you no pleasure, simply because kindness is right; but no one ever did a cruel action simply because cruelty is wrong—only because cruelty was pleasant or useful to him. In other words badness cannot succeed even in being bad in the same way in which goodness is good. Goodness is, so to speak, itself: badness is only spoiled goodness. And there must be something good first before it can be spoiled. We called sadism a sexual perversion; but you must first have the idea of a normal sexuality before you can talk of its being perverted; and you can see which is the perversion, because you can explain the perverted from the normal, and cannot explain the normal from the perverted.
Is it possible to be bad for the mere sake of badness? If not, does that mean there is something at the most fundamental level of reality that is good?
At times, it seems more likely that whatever fundamentally exists without cause would be amoral (neither good nor bad) and not intelligent. It seems unrealistic that something good, or something intelligent, could exist without a cause, as Christians affirm. It almost seems to good to be true that the one thing whose existence is fundamental to all of reality would be good, and loving, and intelligent.
And yet, good seems to be able to exist on its own, but bad "is only spoiled goodness." At the very least, this would make a completely good God more plausible than a completely bad God.
I haven't said anything to defend the existence of an intelligent God, and possibly only a weak defense of a good God. But there's something compelling about this. And Christians take it further: we claim God loves each of us--tiny specs on a tiny spec in a tiny spec in an unimaginably huge universe. And soon, at Christmas, we will celebrate a time when we claim this good, intelligent, loving God actually visited us. Are we crazy? Or is God crazy in our eyes for doing things this way?
