This is the the twenty-sixth post in my Theories of Knowledge and Reality series. Follow the link for more on the series and for links to other entries as they appear. My last post finished up a three-post sub-series on the moral argument for the existence of God. I expect to look at the problem of evil for the next six posts. As one of the most common philosophical reasons not to believe in God (the other being no-evidence arguments), I think the problem of evil deserves twice as much time in class than any of the theistic arguments, and since these posts come from my class notes there's going to be a little more detail in these next posts than there was in some of the last few issues in the series.
[Note: The next several posts on the problem of evil are derived in part from discussions in (1) Gregory E. Ganssle, Thinking About God (2004) InterVarsity Press, (2) Daniel Howard-Snyder, "God, Evil, and Suffering" from Reason for the Hope Within, ed. Michael J. Murray (1999) William B. Eerdmans Publishing Co., pp.76-115, and (3) Peter van Inwagen, "The Magnitude, Duration, and Distribution of Evil: A Theodicy" (1988) in God, Knowledge, and Mystery (1995) Ithaca, NY: Cornell University Press, ch.4, pp. 96-115.]
The problem of evil takes two forms, the logical problem of evil and the evidential problem of evil. This post starts the Logical Problem of Evil. In a couple posts, we'll move on to the evidential problem.
The logical problem of evil begins with three traditional features most theists believe are true of God. The logical problem then proceeds with an argument that such a being would never allow any evil. Given that there is evil, there must be no such being. [The most important presentation of the logical problem of evil is J.L. Mackie's "Evil and Omnipotence", which was published in the journal Mind in 1955.]
Traditionally, God is held to be omnipotent (or all-powerful), omniscient (or all-knowing), and perfectly good. Since there are no limits to what an all-powerful and all-knowing being could do, such a being could prevent evil. Additionally, a perfectly good being would prevent evil as much as possible. Therefore, a being who has all three characteristics would prevent all evil. But there is evil. Therefore, there must be no such being.The logical problem of evil thus takes the existence of God and the existence of evil to lead to a contradiction. There is no way both could be true, according to the argument.