I did good the other day. I poured money into our faltering economy by buying some shoes, and then a sandwich, and then a cup of tea. The Chancellor lowered VAT precisely to encourage this kind of crazy spending. What would be self-indulgent a few months ago is now our civic duty. Extravagance is the new giving. If I really cared, I'd have topped off my spree with an X-Box, a personalised number plate and a night at Spearmint Rhino.

It's probably best not to think about the fact that spending money we didn't have was one of the things that got us into this mess. The first rule of holes might be stop digging, but perhaps that doesn't apply if the hole is so terrifyingly, unprecedentedly, vertiginously deep that it's quicker to keep going down until you reach the other side of the planet.

But if Christmas shopping or eating out now constitute being a do-gooder, where does that leave charities? Screwed is the answer. The Guardian reported last week that projected crunch-induced falls in corporate and private donations will open up 'a £2.3bn black hole' in their finances. And black holes don't have silver linings.

And there are more bad tidings for good causes. A couple of weeks ago, the charity watchdog Intelligent Giving (I presume from the name that it doesn't cover donkey sanctuaries or private schools) criticised charities for the behaviour of their 'chuggers' or charity muggers. These are the pushy, articulate young people who accost you on the street, inevitably when you're holding a bottle of wine and a massive cake, and try and extort a guilt-allaying direct debit.

Well, the terrific news for those of us who've been shamed by them is that the chuggers have been lying. Yes, it turns out the world's fine! No, sorry, they've not been lying to that extent. But some of them have been telling fibs about how they're paid, harassing the uninterested (for which read broke, mean, busy or don't give a shit about lifeboats) and getting people to lie on direct debit forms to help them meet targets. But isn't this just defrauding the rich to give to the poor? They're modern-day Robin Hoods really - and I expect he was working on commission too.

It's difficult not to feel a touch of schadenfreude at the demise of these hectoring representatives of those less fortunate than ourselves. They're the most obvious sign of the increasing aggression and professionalism with which charities now raise money. The regular letter I get from Cancer Research thanking me for my monthly donation of x pounds, and humbly requesting whether I could make it 2x, is clearly generated by a computer that cannot feel gratitude and will never get cancer. If the amount I was giving was beggaring me, if x equalled a million, a billion, a trillion, it would still ask for more because that's what it's programmed to do. It will mine the seam of what I like to think of as generosity, but is actually guilt, as relentlessly as a tungsten carbide drill. The system they're using clearly has no sense of whether or not I'm already 'doing my bit'. I know I'm not, but the fact that they don't makes me think I can be cross with them.

But that doesn't hold argumentative water (and if you've ever tried to hold argumentative water, you'll know that it's just as slippy as the normal kind and it disagrees with your fingers). Why shouldn't charities act with corporate single-mindedness to achieve their goals? After all, unlike a corporation, their goal is the good of mankind.

Still, I can't shake the sentiment that there should be something bumbling and warm, vicarish and jumble-saley about charities. Anything else gets in the way of their gratitude and raises the terrifying spectre that they are blaming me for some of the things that are wrong.

Charities walk a tightrope. The world is awful. Billions suffer crushing hunger, disease, grief and indignity and then die young. I know this in theory, but it's unimaginable. It's like a negative number of apples or a hedge fund: something I can manipulate, multiply and divide things by, but not feel or visualise.

And alongside this pain as unquantifiable as the number of stars in the heavens, the vast majority of Westerners live, even post-credit crunch, in what by comparison amounts to a palace of Versailles made of chocolate and money.

So in some ways the charities should be screaming: 'Pay up, you selfish bastards! Take off the rose-tinted spectacles that some 11-year-old in China has made for you and give us all your cash!'

But that puts people's backs up particularly when many of us don't feel that well off. And why should we live in perpetual guilt? We didn't make the world this way. There's no evidence to suggest that, if the rich and poor of the planet swapped places, the new fortunates would commit to any more than the sighs and affordable direct debits that currently constitute most of our charitable contributions.

All this stirs up conflicting feelings which depress me. I realise that I'm lucky. I earn quite a lot of money and I do give some of it charity. Do I give what I can afford? No, it's worse than that: I give what I won't even miss. I plan to give more. I swear I will.

But I'll never give all I can. I'll never bust a gut to make a difference because the reality is that I don't want to enough. I'm not that good a person, it turns out.

That's the horrible truth that I'm hiding behind irritation at chuggers, cynicism about computer-generated letters and anger at the success of animal charities when humans are suffering. There's plenty that is illogical and enervating about the way our thousands of charities, with their thousands of good causes, behave. But they're trying to do something and, in the end, I haven't got any better ideas; few of us do.

I pay lip service to wanting to change the world, but future historians will note that it was never really in my interest for it to happen.