Moisés Naím / Financial Times

The world feels increasingly dangerous these days. Terrorism and an uncertain economy have greatly heightened our sense of insecurity. The dangers that make us feel insecure are obvious. Less obvious, but perhaps as dangerous, is the world's heightened susceptibility to bad ideas.

Bad ideas that gain currency among the world's powerful are nothing new. But globalisation now allows bad ideas to spread faster and further, leaving much damage and human suffering in their wake. When the public senses an urgent threat - whether terrorism, illegal immigration or unemployment - it often gives those people responsible for dealing with it a blank cheque to do so. Naturally, bad ideas become even more dangerous when massive resources are thrown behind them.

History is full of examples of ideas that become fashionable, only subsequently to fall into disrepute. Some, such as communism or fascism, are big, all-encompassing world visions. Others are smaller. The "dependency theory" of under-development, the "indisputable" superiority of Japanese management, the link between Asian values and superior economic performance, the Laffer curve, "limits to growth" or investing in internet companies with no foreseeable profits - all are ideas that for a while enchanted decision-makers and commentators, then faded out of fashion.

Supplying the Mujahideen in Afghanistan with Stinger missiles during their war against the Soviet Union seemed a much better idea in the 1980s than it does now. Other old ideas, such as "Star Wars", rebranded as national missile defence, are making a comeback. Also, ideas are often quickly displaced as other emergencies drive them out of favour or reality turns against them. In the 1990s, financial crashes made the need for a new "global financial architecture" a popular idea. Today, only a few experts talk about it.

The same happened with the "end of the business cycle", supposedly killed off by the convergence of the information revolution, deeper global economic integration and the ensuing productivity boom. Now the economy has cycled down, no one seems to remember the endless cover stories, business plans, seminars and books inspired by the subject.

Will Europe's Common Agricultural Policy - an old, bad, persistent idea - still be with us years from now or will we then think of it as we now think of the Warsaw Pact? For good reasons, the "war on terrorism" has now become a very popular idea. Will it remain as popular a few years hence as other concerns, threats and surprises compete for the attention of policymakers and their electorates?

Throughout history ideas with policy consequences have been the subject of a cycle of emergence-adoption-rejection (and sometimes re-emergence). But that cycle is now accelerating, contributing to policy instability that may retard the adoption of more effective solutions or, worse, increase the probability that bad ideas become influential. Proven policies that take too long to have an effect are also more vulnerable to being replaced by new, untested initiatives that promise rapid results, often falsely.

This intellectual fragility has been boosted by the cheaper, instant electronic communication that facilitates the global diffusion and discussion of new ideas. Cheaper communication and information make for quicker and broader scrutiny. It is tempting to conclude that the screening of ideas is more rigorous for being truly global. Yet the speed of communication and the volume of information have made scrutiny more cursory as the time available to learn, ponder and react is compressed. The exponential growth of the "noise" within our system of communication makes it harder to differentiate the bad ideas from the better ones. Bad ideas now stand a better chance of becoming accepted, thanks to the accelerated decision-making cycles and the increased public pressures that decision-makers face. Business leaders threatened by hyper-competition, politicians pressed by impatient electorates, or government officials needing to respond rapidly to unprecedented emergencies, they all fuel the demand for new and quick solutions to important problems.

Sooner or later bad ideas are caught and discarded, yet some do find their way into public policy. A few may turn out to influence important decisions for a long while. Most, however, are likely to be shorter-lived now than some of their predecessors in the pantheon of misguided policies. This rapid espousal, swiftly followed by rejection, can only add risk and volatility to an already unstable and dangerous environment.

There are no failsafe, simple solutions to the growing propensity of decision-makers to embrace counterproductive intellectual fads. But as the terrorist attacks on the US have shown, knowing that one is vulnerable is a good first step to finding ways of becoming less so. We need to be as alert to our exposure to bad yet seductive ideas as we are to terrorists.