The Problem of Evil, used by Philo (= Hume) as an argument against the existence of the Judeo-Christian God, is that the following set of statements seems to be inconsistent.

               1.  God is omnipotent.

               2.  God is omniscient.

               3.  God is entirely benevolent.
     Yet
               4.  Evil and suffering exist (and in greater measure than is conceptually required for the existence of goods).

By definition, if God is entirely benevolent He will prevent any suffering that He is able to prevent.  And by definition, if He is omnipotent, he is able to do anything, hence able to prevent any suffering whatever.  Therefore there is no suffering.  (2 rules out the zany possibility that although God is both willing and able to prevent all suffering, there is some suffering He fails to prevent because He just doesn’t know about it.)

    Cleanthes flirts with denying 4.  But that is untenable.  One may take the long view and deny that human suffering is ultimately evil, so one may put quotation marks around “evil” in 4, but that doesn’t make the suffering itself go away.  So we must deny either 1, 2 or 3.  To my knowledge, no one has ever tried to solve the Problem of Evil by denying 2, so that leaves 1 and 3.

    1 is sometimes denied tacitly, by accident: “God has to make/allow us to suffer because [for example] it builds our characters.”  An omnipotent being doesn’t have to do anything.

    1 is more deliberately denied by one version of the Free Will Defense:  Having given human beings free will, God is now unable to control their free actions; evil and suffering result from the free actions of human beings, and cannot be blamed on God.  (Why did He give us the free will in the first place, since it’s had such catastrophic consequences?  Consider the alternative: What would have been the point of creating a clockwork universe, in which there weren’t beings that had free will?)
    Alternately, the Free Will Defender can say that although God is still omnipotent, He chooses not to interfere with the free actions of human beings.  This would mean that He does allow some suffering that He could have prevented, and so it falsifies 3, but for a perhaps defensible reason.  God Himself is still benevolent, and even though there is suffering that He could have prevented, that suffering is not directly His fault, but is to be blamed on the human beings who caused it.

    The main problem with the Free Will Defense is that much evil, particularly the evil that most galls us in the theistic context, is not the result of human action.  The sufferings that drive people to atheism result from horrible diseases or from natural tragedies of the sort referred to in insurance policies as “acts of God.”  So, to be even minimally adequate, the FWD has to be extended.  Natural evils must be seen as the deliberate acts of a powerful free-willed being, the obvious candidate being Satan.  (Hence Hume’s reference on p. 73 to Manichaeanism.)  The literal existence of one or more free-willed unholy nonhuman beings who cause evil and suffering in the world and whose choices often succeed in going against God's will is not widely accepted by theologians, and is hard to believe.  Moreover, if this extension of the FWD is to succeed, it must be total, and cover natural suffering of any sort however trivial.  We would have to take Satan as a practical jokester who, when he is not doing something much worse, goes around giving people hangnails and hemorrhoids; and we would have to take this very literally.  That idea is pretty fanciful.

    It is, I think, more plausible to deny 3, and deny it outright.  To my knowledge, no actual scripture or religious doctrine has held that God is “entirely benevolent” in the sense maintained by Philo’s argument.  No major religion has promised us a rose garden; in fact, Judaism, Christianity, and Islam presuppose that we are going to suffer and go on suffering.  Get used to it and stop whining.

    But now the problem is:

            5.  God is perfectly good.

Can the prevalence of evil and suffering be reconciled with the claim that the universe is governed by a perfectly good superbeing, to Whom on account of His goodness we owe worship and adoration?

    Logically or conceptually, yes.  But there is still hard theological work to be done, to show how or why so much evil and suffering would be visited upon us by a being that is perfectly good.  After all, if you or I (a) saw someone suffering, (b) had the power to relieve that suffering at no cost or trouble to ourselves, but (c) did not relieve it, what would that make us?