If God is unable to prevent evil, then he is not all-powerful.
If God is not willing to prevent evil, then he is not all-good.
If God is both willing and able to prevent evil, then why does evil exist?
Evil is always balanced by Good. Nothing is Evil that does not contain a greater Good.
Sometimes we (human beings, humanity) work out evil to the bitter end.
The problem with Epicurus’ challenge is, what would make anyone think that God is not working actively to end evil, now? What would a God who prevented evil look like? Perhaps God would intervene in each individual circumstance, to get me that parking space I need, to stop that child being run over, to stop an earthquake.
Earthquakes are caused by continents drifting over the asthenosphere, Earth’s magnetic field is caused by movements in the liquid outer core. The magnetosphere protects the Earth from cosmic rays which would otherwise strip away the outer atmosphere, including the ozone layer which protects us from ultraviolet radiation, which damages biological systems. (I’ve been on Wikipedia.) The theological point is that you can’t have one without the other.
The sexual urge that makes the paedophile abuse the child is so strong because the sexual urge needs to be strong to continue the species. You could not have the good without the evil. Note, I do not ask you to see good in the evil, because there is none- the act is abhorrent- but to see it as a side-effect of a necessary thing.
So much evil and suffering in the world is because we are in a state of becoming, not static being.
We die in earthquakes, and we work to support the survivors. The UN takes cholera to Haiti, causing an outbreak killing 8000 and infecting hundreds of thousands, because there is not one clear way of responding to disaster, and we are learning; and because people take risks in disaster relief, as in everything else.
So much evil and suffering in the world is because we pursue the cul-de-sac to the bitter end.
The warmongering of the European powers around 1900 led to the wars of the 20th century, which had evils to make the faithful turn from God. And, after Mutually Assured Destruction- my father was an air raid warden in the 1950s, who never had to perform that task- the Russian Federation and the US reduce their nuclear stockpiles, and are not a hair’s breadth from war- because we did that until we could do it no more.
Progress: not just in technology, but in ways of living together. We live together in mega-cities. We, mostly, avoid killing each other.
Is there anything you imagine a good God should do, which would reduce evil and suffering? I bet I can find some unintended bad consequence in it.
Voltaire satirised my view in Candide: All is for the best in the best of all possible worlds, said Dr Pangloss, following Leibniz. Fortunately, I have Alexander Pope on my side:
Cease then, nor ORDER Imperfection name:
Our proper bliss depends on what we blame.
Know thy own point: This kind, this due degree
Of blindness, weakness, Heav’n bestows on thee.
Submit — In this, or any other sphere,
Secure to be as blest as thou canst bear:
Safe in the hand of one disposing Pow’r,
Or in the natal, or the mortal hour.
All Nature is but Art, unknown to thee;
All Chance, Direction, which thou canst not see;
All Discord, Harmony, not understood;
All partial Evil, universal Good:
And, spite of Pride, in erring Reason’s spite,
One truth is clear, “Whatever IS, is RIGHT.