Think of a number, any number ... £25bn, say, or - go on, be bold - £76bn. Now think of all the ways to spend that cash, such as building new schools and hospitals, boosting international aid, creating a Gates-style foundation to fight Aids or giving grants to charities involved in everything from heritage to hedgehogs.
Instead, this Government is planning to commit all those billions to replacing the Trident missile system - the first figure is the likely initial cost, the other includes its maintenance bills. A submarine can then patrol the waters of the world around the clock, ready to fire atomic missiles at our enemies.
I'm not sure how effective nuclear warfare is against suicide bombers, or whether anyone outside the White House is seriously thinking about turning Tehran into a second Hiroshima unless it behaves. These missiles, first designed for a Cold War now long gone, will never be fired. They also breach our non-proliferation treaty commitment to reduce and then eliminate nuclear weapons.
Many charities, campaigners and church groups are protesting about Trident and offering a useful net resource at bigtridentdebate.org.uk. But for the moment let's forget that, as a weapon, it's a useless, illegal anachronism.
Concentrate on the cash instead.
Without asking you, the Government has already spent many millions of pounds on preparations for a new Trident. Even if Gordon Brown can mortgage future generations with the mother of all private finance initiatives, those billions and maybe more - what government contract comes in on time or budget? - will have to be found by increased taxation, public sector cutbacks or both.
Alternatively, one way New Labour could raise funds for new Trident could be, once again, to divert gamblers' 'good causes' cash. Atomic Lottery anyone? All this can only harm the voluntary sector and those in need; if used for other purposes, all that cash could save millions of lives.
But should the third sector care about Trident?
You may be concerned, thinking that child health, cancer research or conservation of our environment deserve the cash more. Or you might actually believe Trident is worth every penny.
Either way, don't worry. Just as New Labour's own conference was barred from discussing Trident and parliamentary debate looks set to be curtailed, your views about your 'defence' are, of course, irrelevant.