John Mackie has presented one of the most popular formulations of the problem of evil, it can be accessed here. I will not reproduce all of his arguments, but he attempts to argue that the existence of a totally good, all-powerful God is incompatible with the existence of evil.
Of course, many believers have put forward objections to these arguments over the centuries, and so Mackie attempts to show why those objections fail. I think one of these attempts is no good, and I will briefly explain why.
One of the primary tools of the theist here is the appeal to the higher order good. God may allow the evil of fear to exist so that the higher order good courage might exist, for example. Clearly, courage would not exist without fear, and courage is good. Perhaps in God’s mind, the goodness of courage makes the evil of fear worth it. I don’t intend to imply that we can somehow measure the goodness of the situations and compare them numerically, I certainly don’t want to endorse utilitarianism. I only need to say that there is something about the higher order good case that justifies the lower order evil.
Mackie responds that sure, we can say that. But then we also have 2nd order evils, perhaps cowardice. And now we need to justify the second order evil. And of course, the tempting route for the theist is to justify it using perhaps a third order good. But Mackie says (denoting a second order evil by “evil (2)”):
But even if evil (2) could be explained in this way, it is fairly clear that there would be third order evils contrasting with this third order good: and we should be well on the way to an infinite regress, where the solution of a problem of evil, stated in terms of evil (n), indicated the existence of an evil (n + 1), and a farther problem to be solved.
I think this response is not very good. I think Mackie has assumed without justification that there exist n’th order evils that need to be explained. But it’s not clear to me that that is the case. I couldn’t tell you how high in order evils go, but I don’t think it’s reasonable to say that good could go a level higher. It’s not surprising that there would be an asymmetry between good and evil, where good is in some sense “more real” than evil. Many classical theologians have formulated notions of good that are convertible with being, so goodness is being and being is goodness. And under an idea like this, we would be shocked to see levels of evil for each corresponding level of good. Eventually, we’d expect to get to a point where good was simply higher than evil, and no equivalent high order of evil existed. There is a sense in which good is “bigger” than evil.
Mackie then moves on to discuss a particular case of the higher order good: free will. Being a Calvinist I am not particularly interested in making a free will defence when it comes to the problem of evil, nor defending a libertarian free will from Mackie’s objections in the paper. But I think this flaw with higher order goods is sufficient for the Christian to remain justified in their beliefs.