The problem of evil, briefly stated, involves the conflict between ourexperience of evil in the world and the traditional notion of an all-good,all-knowing, all-powerful God. This problem is taken seriously by mostbelievers as presenting an intense challenge to their beliefs, and is theusual grounds offered by atheists for their atheism. The atheist arguesas follows:
God is all-good, all-knowing, and all-powerful by definition, but eviloccurs in the world. There are natural disasters, degenerative infants'diseases such as Tay-Sachs, and the evil that is done unto people by peoplewho are evil, mad, insane, misled, or frightened. If there is a God, Sheor He either makes these things happen, permits these things to happen,or cannot prevent them from happening.
If She or He makes them happen it is either knowingly or unknowingly;if unknowingly, then She or He [again by definition is not God who is all-knowing],but if She or He knows, God is evil.
If God permits these things, it is a like case, a case of what we wouldcall cruelty if a person did it, i.e., to allow great evil to transpirewhich She or He could have easily prevented if God were all-powerful andaware.
If She or He cannot prevent these things, then She or He is not all-powerful,and therefore [again, by definition] not God.
The traditional enterprise of trying to justify God and belief in God'sexistence despite our experience of evil is called theodicy, fromthe Greek words for God [theos] and Justice [di`keh]. Theseresponses take many forms, some focus on our concept of Evil, others onour ideas about God. Still others question the enterprise of theodicy itself.
Traditional Orthodox theodicies usually proceed by arguing that whatwe perceive as evil is not really evil. Some do this by trying to showthat evil is merely the absence of good. Others argue that suffering isa form of divine pedagogy or punishment [this approach goes back at leastas far as the interlocutors speeches in the Book of Job]. Many traditionalistsas well as modernists uses the free-will defense in which they argue thatevil is a consequence of people's choices, and that we, not God, are toblame for it. They usually go on to argue that the presence of free-willis such a great good that there is no evil which would justify deprivingpeople of it.
There are traditionalists and modernists who will move to the natureand attributes of God in their attempts to deal with this problem. Someargue that God is somehow too perfect to know what is going on with particularevents and people like ourselves. They claim that there is only a generalprovidence [that things in general are just and good]. Of those who takethis view, some argue that one must identify intellectually with the abstractin order to attain to the protection of general providence [many hold thatthis is the view of Maimonides].
Among the non-orthodox, there are those who argue that God simply isnot powerful enough to prevent evil, that though we should credit God forthe good that takes place, evil is to be explained in terms of other forces.This is the view of some of the "personalists" such as Brightman,and Whitehead; a readable presentation can be found in Harold Kushner'sWhen Bad Things Happen to Good People.
One other view, which seems to have its proponents in some of the Biblicalliterature, has been argued recently in the work of Walter Kaufmann. Accordingto this position, a pure monotheist has no choice but to blame God forthe bad which takes place just as one praises God for the good.
Another radical response involves arguing that it is not God's existencewhich is important, but the high ideals which we identify with God, thatit is our task to realize the good and to fight evil.
Another approach taken by many traditionalists and modernists alikeis that of silence. For some, silence on this question is the best onecan do. Others feel that silence is the only morally acceptable alternative,given the events of history. They hold that to defend God, given our experience,comes perilously close to defending evil. Elie Wiesel, for example, ina play (I think it's The Trial of God) about God being tried forevents of the Holocaust, assigns the role of God's defender, the divinedefense attorney, as it were, to Satan.
For more on God judging, please see Eliezer Segal's online essay
Four novels which suggest fruitful responses to the problem are:
For a very brief itemization of attempts to explain the presence ofhuman evil,
see my notes on anthropodicy.