Why does God allow evil?

'Rushing in where angels fear to tread' springs to mind, but in for a penny... ;-)

If God is perfect (and if he isn't, he's not God), why does evil exist and why does God allow it to continue?

A few quick provisos:

• A blog post can't do more than skim the surface of such enormous issues
  
• There are probably as many ways of answering the questions as there are thinkers about it
  
• People of faith have wrestled with these issues for millennia and the struggle has often enriched their faith without producing any simple answers
• A lot depends on our definitions/understanding of 'good' and 'evil', which there's not room for here. But for example, is all pain and even all suffering actually evil, or merely very unpleasant and difficult? Is death always and inherently bad? Can destruction sometimes be good (say of a cancer)?
  
• Ultimately, evil is not a riddle to be solved but a reality to be dealt with.
  

My own (tentative and provisional) view is that Evil is an unavoidable potential inherent in Good. Evil is not a separate entity from Good; it is merely Good corrupted, twisted, misused, misplaced or attenuated. It is the shadow side of Good: where there is freedom to bless, there must also be freedom to curse; where there is freedom to build, there must also be freedom to destroy, and so on. And as noted above, sometimes destruction (e.g. of a cancer) may be a right and necessary and thing. 

So God did not create or plan evil, but evil was inherent as a potentiality within the good.

Furthermore, Christian theology holds that God wanted morally free, responsible agents whose actions could have genuine significance; who could genuinely love and embrace the good out of free choice. Again, this implies freedom not to act this way; the potential for good inherently includes the potential for not-good, or less-than-good, or good twisted.

At some point then the potentiality for evil becomes the reality of evil, infecting and corrupting the goodness of the cosmos and perhaps even of all things in it. When this happens, one option would be for God to wipe everything out and start again - a bit like a writer ripping up a whole manuscript because of a flaw running through all of it. But this is not the action of one who truly, passionately loves. In all the corrupted things and creatures there is still so much of the original good, and God chooses the long, slow, painful path of redemption and restoration - ultimately even involving his own self-sacrifice and death - to heal the damaged creation. This is, more or less, the Christian story.

In Matthew 13:14-29 Jesus tells a story about a farmer who planted a field of wheat, but an enemy came and planted weeds among the wheat. Rather than trying to pull up the weeds and risk pulling up the good wheat too, the farmer let the two grow side by side until harvest time when they could be separated without damage. This is a picture not only of the cosmos but of everything in it, including our own hearts - good and evil are for the moment inextricably entwined, and God will not risk destroying the good by ripping out the evil. I for one am very grateful for this, as I know too well that many of my thoughts, attitudes, words and deeds do not put me unqualifiedly in the 'good' camp.

Anyway, these are all just my suggestions, not some definitive statement.