IT is as easy to state as it is to understand:

Islamic State (IS) must be stopped. Opinions against the proposition constitute a very small minority. The question is not one of ends, but of means. The IS issue does not involve good intentions, of which the world enjoys its usual surplus, but the consequences of what glib politicians call "action".

For a winner of the Nobel Peace Prize who also happens to be President of the United States, things are especially tricky. Barack Obama and his allies do not have to re-invent the fictions of George W Bush and Tony Blair to excuse intervention in the Middle East. The nature of the IS alliance is understood. The beheadings, the mass executions, the hordes of refugees, the threats of a regional conflagration, the risk of an all-out Sunni-Shia war: these can be documented. There is also the matter of oil, too.

You can make a moral case, or several moral cases, for becoming involved. You could say, at the risk of self-serving duplicity, that the West cannot leave Iraq in the lurch now, given the hideous mess created by the US and UK when they chose to depose Saddam Hussein in 2003. You could also argue, with justice, that the latest perversion of organised religion cannot be allowed to stand. Conversion, if that is the word, by machete and gun should no longer be tolerable.

Moral philosophy lays traps for the mendacious and the well-meaning alike. Where do you stand if the attempt to right a wrong only makes things worse? You could throw up your hands and step aside. You could say that the affairs of strangers should never be our business. If you happen to be American, you could remind yourself that any attempt to police the world is folly, especially when it is laced with arrogance and driven by self-interest. Or you could think twice.

That would involve thinking about the lessons we - as ever, a preposition loosely applied - were supposed to have learned. What do we know about bombing campaigns in the Middle East? First, that they tend to kill the innocent and the guilty alike. Part of the indictment against Bush and Blair is that at least 115,000 of the civilians who were supposed to be liberated from dictatorship - and probably a great many more - died thanks to the West's invasion. Bombs and missiles do not discriminate.

They have a nasty habit, too, of producing a reaction. In Iraq, after the first attempt, the West was pleased to call the local reception an insurgency. When democracy was declared and the US-UK alliance got the hell out, the ground was made fertile for IS and much else besides. Just to help matters along, our favoured Baghdad regime turned out to be brutal, sectarian and corrupt. Benevolent hypocrites in the West, with their local proxies, gave the jihadis every invitation.

Now the cry goes up, from the White House to the United Nations to the Commons, to smash this year's threat to civilisation. IS, with ostentatious brutality, seems happy enough to play along with that. For anyone trying to negotiate the moral maze, there might be a clue in the fact. There is a bigger clue: we are out to eradicate thugs we used to arm in the struggle against that other thug, Syria's president Bashar al-Assad. As plans go, it's a little off. It involves the kind of thinking that kept Saddam in power for years.

Another of moral philosophy's little wrinkles becomes evident, meanwhile. Dealing with the bad guys does not, of itself, make us good guys, not to the millions of innocent bystanders who find themselves on the receiving end of bombs, missiles and drone strikes. It's hard to be grateful for democracy when your family is dead. It's hard to trust those who lay waste your world to justify their fine sentiments. You might not adore IS or a Saddam as a result. But you will struggle to understand the phrase "Western benefactors".

Still, keep it simple: the jihadis in Iraq and Syria must be stopped. If not, worse will follow; more innocents will suffer; inaction will leave us complicit, in one of those sins of omission, in barbarous lunacy. So is bombardment the best we can do? Or has that just become a habit, our favourite son et lumiere now the military-industrial complex is our global government in all but name? Note that even the Nobel Prize-winner, he who won an election promising to halt lies and madness, cannot think of anything better.

There's hypocrisy in that. It courses through the Western TV news audience as much as it courses through Obama and David Cameron when they seek to justify "action". Killing innocents while we deal with the IS barbarians is acceptable; risking our own "boots on the ground" is forbidden by opinion polls. These double standards are compounded when Blair, who gave the UK a rational aversion to foreign adventures, demands boots and young men to fill those boots.

If we won't risk our own, we shouldn't risk the lives of innocents in Syria and Iraq with our bombs: as ethical propositions go, that one should be obvious. Yet we know two further things. First, IS will not be stopped with a peace conference in a fancy Swiss resort. The movement thrives on fear and extreme, implacable violence. Its leaders have no interest in being reasonable, if they even understand the word. The war against them has become unavoidable, for democrats and the Middle East's tin-pot regimes alike.

The second thing we know, however, is that the West's attempts to impose its will produce horrors. It no longer matters whether the intentions are good or bad. The intervention by the US, UK and France against Gaddafi in Libya remains a hellish case in point. No-one wants to discuss that piece in the Middle East jigsaw right now because of the miserable precedent it sets. We stepped in, with our military might, to aid citizen rebels on the verge of defeat. Today, that liberated country is in a bloody shambles. And this despite the fact that very few of those Western boots touched Libyan ground.

Give the Kurds all they require. Give the latest Iraqi government such help as it can handle. Let local states - those reliable buyers of Western kit - do what they can until they attempt to grab some petty advantage. Meanwhile, reach an overdue accommodation with Iran, whose self-interest is evident, and tell the Israelis that no mischief will be tolerated. If America and the West cannot do these things, they have no business claiming a right or a duty to "lead" anyone.

There are plenty of air forces in the Middle East; the self-appointed cavalry are not required. If there is a serious desire to avoid the creation of another generation of jihadis, in fact, the trick might be to avoid sounding "Boots and Saddles" whenever one strategic catastrophe gives way to another. Sometimes history is a far better teacher than moral philosophy.