Oh very well (he says, sighing a little and brushing to one side in a gesture of weary resignation the flopping fringe he hasn't got) I suppose someone's got to save the world.
First we need to define terms. Let's begin with the noun, the substantive, the only stand-upon we have, the world. That does not seem hard to define. The world is this iron-hearted lump of rock that keeps going round the sun. Do we agree on that? Good.
Then what's all this about saving it? The world is not threatened. It is in stable orbit and every indication is that it will remain that way for a very long time indeed. Eventually, of course, the sun will consume both the earth and itself, but that is far too far into the future for us to bother about, and besides, potent though we newspaper columnists are, that problem remains beyond us.
So it is clear that when people speak of saving the world, they have a different definition in mind. Let us suppose then that they mean the habitat that has developed on the globe's surface - the atmosphere, the sea and land, the forests, lakes and rivers, the ice and snow, the deserts and the mountain ranges, along with the creatures that have evolved to inhabit them, the fishes and the birds, the scaly and the furry beasts, the plants and insects, fungi and bacteria, the whole happenstance of boiling teeming life.
If this is how we define the world that we want to save then the problem is a simple one. This world is clearly under threat. The three main threats to it are the rapid change of climate, the rapid loss of wilderness and the rapid growth of pollution. All three have one thing in common - us. We've caused them all. So to save this world is simple. We just have to get rid of people.
That, however, once again, does not seem to be what people mean when they speak of saving the world. The world they want saved is one with us in it, otherwise what's the point?
So let's try defining it as a world in which human beings and the natural kingdom live side by side, if not in symbiotic harmony, at least in enduring mutual tolerance. And if that is our agreed definition then we must now come to the other word we began with, which is the verb. The verb is to save. To save is to retain. And you can only retain something you already have. But we don't have a world as just defined. Human beings and the natural kingdom don't live in enduring mutual tolerance. One's destroying the other.
The notion of a balanced and harmonious world has long occupied a place in the human psyche. In the Christian tradition we call it Eden. But it has never existed because we always bugger things up. Consider these islands for example. When the first human beings arrived a thousand years ago, bush and moa abounded. Five hundred years later a lot of bush and every moa was gone. And it took only a few thousand of us to do that.
To summarise, then, the notion of saving the world is a fashionable catch cry. But it has neither rigour nor thought behind it because the world we'd like to save does not exist.
Nevertheless there was a time when we human beings did less damage, when our influence was only locally rather than globally catastrophic. That time was when there were fewer of us.
Drink up, longevity and puritanism don't mix
It took tens of thousands of years of relatively harmless existence for the human population to reach a billion, around the beginning of the 19th century. But since then we've added another six billion or so. Just in my lifetime the population of the earth has doubled. And that period coincides with the worst harm to the natural world, the greatest number of extinctions.
So it seems inescapable that if we're to save what's left of the planet's surface we must reduce our numbers. This is sure to happen in the end through disease, war, famine or natural catastrophe, but we already have the technology to do it in a less drastic manner.
If we limited every couple on earth to a maximum of two children, the population would soon shrink and most problems would begin to solve themselves. The world as we'd like to see it would revive like Chernobyl.
There. Next week, the afterlife. (Aw, don't tell me you've already guessed. Okay. UFOs then).