Is the eye-worm the knock-down blow to Christian faith that atheists believe it is? Stephen Fry seems to think so. In an interview with Irish TV host Gay Byrne last week, Fry was asked what he would say to God at the pearly gates of heaven. The ensuing rant – articulate, polite but savage – was widely shared. "I'll say, 'Bone cancer in children? What's that about?' How dare you? How dare you create a world in which there is such misery that is not our fault? It's not right. It's utterly, utterly evil."

And the eye-worm? It's this to which he refers when he says: "Yes the world is very splendid but it has in it insects whose whole life cycle is to burrow into the eyes of children and make them blind. It eats outwards from the eyes. Why?"

So do the worm, and the bone cancer, and all the other ghastly conditions that disfigure the biological world – not to mention the multitude of horrors human beings inflict on other members of their own species – make it impossible for a reasonable person to believe? 

Tell me about this worm, then.

He seems to have borrowed it, so to speak, from David Attenborough, who said in 2009 that he got hate mail from creationists complaining that he didn't credit God enough for the wonders of nature. He told the Radio Times: "I always reply by saying that I think of a little child in east Africa with a worm burrowing through his eyeball. The worm cannot live in any other way, except by burrowing through eyeballs."

In fact it seems that no such worm exists. According to the New Scientist, Attenborough probably meant the Loa Loa eye-worm, which it says are "endemic to the swamps and rain forests of central and west Africa, and, contrary to my horror-movie vision of bursting eyeballs, are rarely life-threatening and no more harmful than the myriad other human parasites in the region".

So, no problem? 

Hardly. Fry may be weak on biology, but that isn't to say that there aren't nasty, nasty things out there. For instance another candidate is Onchocerca volvulus, a parasitic worm that causes 'river-blindness'. It is spread by a biting fly and causes a range of horrific conditions including blindness; whole communities can be affected and there are thought to be around 37 million infections worldwide.

Parasites sound absolutely horrible.

They are, and the idea that something depends for its life on living on and weakening or killing another creature, sometimes effectively eating it alive, presents something of a challenge for theology. However, Christian scientists point out that in the case of animal or insect suffering we shouldn't be swayed too much by the 'yuck' factor: lots of creatures depend for their survival on the deaths of others, after all.

But what about human suffering?

Indeed. Fry also mentioned bone cancer, for instance. It is the idea, no less powerful for being very common, that the depth and extent of human suffering makes any idea that a good and loving God could exist untenable.

It's a pretty strong case, isn't it?

You make a very important point.

Really?

Yes. One of the problems with what is called "theodicy" – justifying the righteousness of God in the face of evil – is that many of his defenders don't recognise the power of the contrary argument. So their attempts work within the closed system of religion, but don't carry the slightest conviction outside it.

Such as?

There's the "Narnia defence", for instance: in C S Lewis's "The Magician's Nephew", Digory's mother is dying of cancer and Aslan, the Christ-figure, doesn't heal her but cries "great shining tears". The idea is that God doesn't stand aloof from suffering, but mourns with us. That's all very well, but it cuts no ice with the mother of the child with bone cancer: she just wants her child to get better. Sympathy, divine or human, doesn't do that.

Any others?

Lots. Pointing to the death of Christ is another: preachers like to say that when Jesus was crucified God was sharing in the suffering of his creation. It is a powerful preaching point from a devotional point of view, but as an argument defending the goodness of God it makes no sense at all. If your child is infected with Onchocerca volvulus you don't want a doctor to say, "Look, I've got it too!" You want her to cure it.

You are a Reverend, aren't you?

Indeed, and I'm not saying there are no answers, just that we need to think very hard before we presume to offer them. Job's three comforters were arguably at their wisest when they sat with him and said nothing at all; things went downhill the moment they opened their mouths.

On the other hand, saying nothing is not really an option, because these issues are so sharp and painful. This is particularly the case with diseases which are no one's fault, but just built in to the nature of things – Onchocerca volvulus again – but in reality all innocent suffering poses the same question. Either God could stop it and doesn't want to, in which case he isn't wholly good, or wants to and can't, in which case he isn't all-powerful.

That seems quite hard to answer.

It is. So some theologians have tried to re-imagine what omnipotence actually means. For instance, a few years ago the evangelical theologian Clark Pinnock wrote a book called 'Most Moved Mover: A theology of God's Openness' in 2001. He argued that the conventional idea of God comes from Greek philosophy and that the Old Testament has a much more "human" conception of him; he doesn't have everything mapped out, and knows what might happen rather than what will. Not everyone agrees, obviously; it is rather too theologically daring for most evangelicals.

What are the alternatives, though?

There are those who argue that God intended the world to be good and that humans spoiled it through the Fall, but this doesn't solve anything. Even if you believe in a literal Fall in 4004 BC, God still had to allow it to happen, knowing all the dreadful consequences that would follow. (There is also the small point that Genesis 3 doesn't mention disease, parasites etc, aside from the scientific objections to this view.)

If you don't, then evolution over aeons is God's chosen method of creation, and death and disease are built into that. That's quite hard: for instance, Tennyson in his poem 'In Memoriam' wrote not long after Darwin about those "Who trusted God was love indeed/ And love Creation's final law/ Tho' Nature, red in tooth and claw/ With ravine, shriek'd against his creed" – the natural world is not aways a warm and cuddly place.

But couldn't there have been evolution without parasites like Onchocerca volvulus?

That is problematic, to say the least. The only way that we can conceive of developed life evolving is through the mechanism that we actually have. You can't just say "I don't like this bit" and magic it out of biology, any more than you can say that earthquakes won't knock down cities or fires won't burn people: physical laws work whether we want them to or not. Knowing what we do of the laws of the physical universe, it is arguable that this is the only one that he could create.

But don't we believe in miracles?

Most Christians do, but most would say that they're rare. We can't expect God to catch us in mid-air if we fall off a cliff. However, admitting even the possibility of miracles is a problem, because you have to ask why they are rare – so it's back to square one. God has chosen to create a world in which it's possible for really bad things to happen, as well as really good things.

So a Christian has to say something like, "Well, he must have thought that it would be worth it, taking the long view and all in all." A world in which there is freedom for human beings to grow and change, to meet and overcome challenges, and in which the depth of suffering calls out the height of love and self-sacrifice, is better than the world not existing at all.

I still worry about Onchocerca volvulus.

You should, because one of the problems with arguments like this is that they tend to lose all their traction when they come up against real people in real pain. But arguably, when we're face to face with such things, our instinct shouldn't be to discuss them, but to get angry and do something about them. Part of our discipleship is to work for human flourishing in body, mind and spirit: we should make the world better, as far as we possibly can.

You seem to have fairly limited aims when it comes to the whole problem of evil thing.

Yes. If anyone says that they've solved it, don't believe them. The best that theodicy can do is to create a space for faith to exist without it being completely incoherent or irrational. In that space it can grow stronger, so that when personal challenges come we can meet them still believing in a God of love. We shouldn't expect to be exempt from the laws of the natural world, but sickness and death don't mean that God doesn't care. Instead, we should try to learn and grow through what happens. And it's alright to be angry - there's plenty of anger in the Psalms, after all - and it's alright to grieve.

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