As the financial balloon dips and the ocean licks the basket, out goes that heavy marble bust of Adam Smith - splash. This, it seems, is no time for ideology. Capitalism? How fast do isms lose their allure as brine slaps against wicker and the prospect of a dunking grows.

To those of us who have admired America as the spiritual home of laissez faire capitalism it has come as a shock this week to observe with how little apology or even backward glance the guiding free-market principles of risk and reward have been dumped in a crisis. Without Fannie Mae and Freddie Mac, Americans would have found it harder to buy houses. But without General Motors they would lose their jobs. So what if GM hits the rocks? Where do you interrupt the logic of intervention? In recent weeks the answer, increasingly, is that you just do.

Out of the window with ideology: ours is an age that has grown impatient with belief-systems in politics. Long before this week's crisis, the phrase “what works” was gaining currency in politics and economics, and it is more than a decade since around Westminster dining tables it has been considered smart to profess to any other dominating conviction. To modern men and women only “outcomes” count.

We are all for individual liberty until... All free-marketeers until... All for jury trials until... We all believe in equality until... All for respecting other nations' sovereignty until... All for moral hazard until...

The subliminal implication is that doctrines, like crucifixes, command a reverential nod, but are to right-thinking people always trumped by practical needs.

It was Tony Blair who popularised the language of “what works”, and in his premiership and in the shambles that has followed will be found many striking examples of the new anti-ideology ideology. But Mr Blair did not invent the tendency. I'm far from suggesting that the retreat from absolutes whenever things get hot is a feature of our age or of new Labour alone. “Needs must when the Devil drives” is an ancient proverb, and in the face of immediate pressure it's a natural human tendency to set theory aside. Central to the aims of the Cameron Conservatives' detoxification strategy has been to stop looking ideological - or, as the phrase goes, “obsessive about”, anything you could call a dominating political idea.

Except, of course, what works. The very unspecificity of our era's political buzzwords - “fairness”, “caring”, “delivering” and “reaching out” testifies to a modern horror at any philosophy that might hinder anyone from doing what looks like common sense in the immediate circumstance. Wait for a special measure called the Short-Selling (Prohibition) Bill, which will be received to cheers and later flounder as legal draughtsmen attempt to distinguish between the boo-practice of the hour and the idea that we might buy or sell according to whether we think an item is likely to rise or fall in value, and hope by our own actions to reinforce that trend. It's what markets do. They bet.

These, however, are considerations of general principle, and general principle - the abstracting from particular events of the underlying logic linking them to other, future and as yet unknown events - has become the orphan child of our politics, disowned by Right, Left and Centre.

How long did our commitment to individual liberty and due process survive two large explosions in New York? How long did the Labour Party's historic belief in the equality of man survive the realisation that the late-20th-century middle-class voter was unpersuaded? How long did Mr Blair's youthful belief in international law and the UN Charter survive his introduction to a very bad dictator in Iraq who had gassed people? How long did Gordon Brown's commitment to a referendum on the Lisbon treaty survive the news that he would not win the vote?

But the “what works” mantra is not always cynical, nor does it lack supporting arguments. I'm far from thinking I know enough about the world's financial markets to be sure that there was any alternative this week to massive state intervention. The instinct to staunch the immediate haemorrhage is often well-founded.

As a laissez faire Conservative I opposed the introduction of the minimum wage, but wouldn't now suggest its abolition - because it seems to work. Ditto compulsory seatbelts. On grounds of free speech I would have objected to the Race Relations Act were it not for those landlords' signs, “No coloureds, no Irish”, that made us libertarians feel like heartless quibblers. A respect for the immediate and obvious as opposed to the theoretical may be healthy, and what we English call common sense.

But still I feel for that orphan child of 2008: general principle. Its neglect is part of the dumbing-down of our political culture. So I'll try to say why it matters.

To be able to abstract from a particular case the general principles applicable to other cases lies at the heart not just of lawmaking, but human intelligence. You may say: “Who cares about comparability so long as we get the best result in each case?” The answer is that general principle speaks not just to the head but to the anxieties, greeds and calculations that drive us; and to the memory too. Paradoxically, the heart may make logical connections that the head fails to register. Hence that sincere scream of protest from the XL passenger stranded in Miami: that the Government should bring her home because it wasn't her fault.

The smallest tot, barely able to talk, can be electrified by indignation at the unequal application of a rule. As one of the higher orders of animal she's hard-wired to plan ahead, and so seeks predictability in her dealings. She wants rules.

Ideologies are ideas systems which, when applied within a society, justify rules. Ideology allows citizens to get a grip on the guiding principles. If (when strong anxieties or sympathies are aroused) the rules are set aside, the immediate human response is often of huge relief; but this has been bought at a cost - slight and almost imperceptible - to people's underlying confidence in the principled framework into which national decisions should fit.

Impulses, greeds, hopes, fears and rules form a whole ecology, linked beneath the surface. At a time when we are coming to understand how our planet's natural environment is so subtly cross-levered that any intervention has hidden consequences, we are forgetting our grasp of the interlocking intellectual framework that should guide public affairs. Doctrine, ideology, political philosophy... to be “in the grip” of these is now thought suspect.

We should beware. There remains one ideology to which most still subscribe. It is called the democratic ideal. No less a belief system than any of the others, it may not finally be proof against the aw-shucks charm of that mindless, shoulder-shrugging deferral to “what works”.

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