Wheat and tares

A recent exchange I had with an unbeliever on Facebook:

Its impossible to explain away unnecessary suffering like child cancer without appealing to unsatisfying answers like 'its a mystery' or 'child cancer is part of God's plan'. We can all imagine a world in which unnecessary suffering like child cancer does not exist yet freewill does. Thus such suffering is gratuitous and unnecessary.

I don't subscribe to the freewill defense. That said, your objection is superficial. Sure, we can all imagine a world without children dying of cancer. The problem is that people who imagine a better world mentally eliminate the evils while leaving everything else in place, including the goods. But removing some evils removes second-order goods that are contingent on the existence of the underlying evils. So that's the dilemma. 

To take your own example, childhood cancer is an opportunity to develop certain virtues which would never exist in an idyllic world. 

Likewise, if a couple had a child who dies of cancer, they may have a replacement child to compensate. And the replacement child may have kids of his own, and grandkids.

That compensatory good would not exist if the older child hadn't died. So it's a tradeoff between one life and another, or one set of lives and another. Moreover, the cancer created the opportunity for two children to exist instead of one.

How is it NECESSARY that we need unnecessary suffering to have goodness?

That's a loaded question since you smuggled your own assumption into the formulation of the question. Sure, it's tautology to say unnecessary suffering is unnecessary, but that simply begs the question regarding the existence of gratuitous suffering.

but i'm saying CUT OUT THE MIDDLE MAN. Have the good without the tragedy.

But it wouldn't be the same good. Evil is gratuitous if God could prevent it without losing some distinctive good or permitting some equally grave or greater evil. 

Once again, the cancer analogy. You are saying we shouldn't eliminate cancer or polio because of all the secondary good it has. Why can't that good happen without the cancer or polio?

i) The argument from evil is not about what humans should do but about what God (allegedly) should do. God and humans don't have the same responsibilities. God has foreknowledge and counterfactual knowledge. We don't. Therefore–unlike God–we're in no position to consider long-term outcomes. 

Likewise, as social creatures, we have emotional investments that God does not. 

There's some overlap between divine goodness and human goodness, but they don't overlap. 

ii) Would a world in which children never die be a better world? Better in some respects. But better for whom?

If humans were immortal from the outset, then humans would have to stop reproducing after a few generations. That means most humans who exist in a world with infant morality wouldn't exist. Is it better for them never to have the opportunity to enjoy the gift of life?

It may be better for the children who don't die, but it's hardly better for the children whose existence is edged out under that alternate scenario. 

Every child is unique. Those are incommensurable goods. 

iii) Moreover, a world in which no one died from illness or senescence would be a world chockfull of selfish people who'd never risk their life or health to save someone else from, say, a house fire. There'd be too much to lose. 

iv) A future without childhood cancer might be better, but a past without childhood cancer wouldn't be better for the people you care about, since they wouldn't exist. Better relative to whom? It is better for your loved ones if the past is the same up to their birth and maturity, then diverges after they have their prime of life. 

v) Unfortunately, there's a human tendency to take friends and family for granted. We act as though they will always be available. There are so many lost opportunities.

When, however, a friend or family member gets cancer, we make up for lost time. That intensifies the remaining time we have with them. 

vi) Regarding polio, many healthy people squander the gift of life. To be disabled can prompt people to make the most of fewer opportunities. 

vii) Suppose one teenage boy has polio while another teenage boy from the same general vicinity is a football star. He comes from a dirty poor family. He's counting on a football scholarship to pay his way through college and make a better life for himself.

Now let's change a variable. Suppose the other boy doesn't have polio, and he's a better athlete. The boy from the poor family who was banking on a football scholarship loses that opportunity. 

In each of these scenarios, there are tradeoffs. Each scenario has second-order goods. By eliminating the evil, you eliminate a distinctive good. Evil can be both beneficial and harmful. 

vii) In general, it's good for humans to work to eradicate polio. But there are situations where we wouldn't eliminate a short-term evil if we knew the end-result. Normal people will avoid actions that harm their loves ones. Yet what is good for my beloved may be bad for your beloved, or vice versa.

I have greater responsibilities for my family than I have for your family. By contrast, God doesn't have greater responsibilities for any particular family.

How God balances out good and evil is different from how a conscientious human might.

You've got a hidden assumption in there. Its like the old cliche of you can't have joy without suffering. Well yes, yes you can.

Since I didn't use that in my argument, you're objection misses the target.

but must appeal to a mystery (God knows all counterfactuals but we don't so it must be hiding in that knowledge!) and have no reason to believe it besides the fact that rejecting it is really damaging to your view on God.

Responsible humans would sometimes make difference choices if they knew the long-terms consequences of their actions. There's nothing mysterious about that principle. Naturally, God has a different perspective. The proverbial God's-eye view.

Well I can easily imagine a world identical to ours WITHOUT child cancer.

Actually, you can't. A world without childhood cancer would not be identical to ours. A world without childhood cancer with have different genealogies. 

It's like the parable of the wheat and the tares (Mt 13:24-30,36-43). Human lives are mutually entangled. It isn't possible to uproot the tares without uprooting some of the wheat. Pull out the evil and you pull out some of the good that's intertwined with the evil.