Are alternative therapies really just placebos, as a group of senior doctors claim? For many people, this question appears rather academic. What does it matter, they may ask, if an alternative therapy is just a placebo, so long as it works?

From a purely therapeutic point of view, of course, it doesn't really matter. But from a scientific point of view, it certainly does.

Many alternative therapies are not presented simply as therapeutic techniques but rather come bundled up with a particular theory as to how the technique works. The needling technique of acupuncture, for example, is often (though not always) taught alongside the theories of traditional Chinese medicine, according to which a special kind of energy known as "qi" flows along channels known as meridians. The art of prescribing homeopathic remedies is taught alongside other strange ideas, such as the theory that dilution makes medicines more potent, and the claim that water has a kind of "memory".

These bizarre notions are, however, completely at odds with everything we know about physics, chemistry and biology. Despite hundreds of years of anatomical dissection and decades of microbiology, nobody has ever once observed a meridian or measured a quantum of qi. And, despite claims to the contrary, nobody has ever succeeded in recording the memory of water on a computer's hard disk.

It is the association of alternative therapies with these crackpot theories that is responsible for the continuing schism between orthodox and complementary medicine. If the techniques of alternative medicine could be separated from the dubious theories that sometimes accompany them, the way would be open to a much more profound dialogue between orthodox and complementary practitioners, and a greater integration of conventional and complementary healthcare.

There is always the possibility, of course, that doing away with the crackpot theories that provide alternative therapies with some of their appeal may actually rob them of their effectiveness, by destroying the vital belief that enables these therapies to mobilise the placebo response. In such cases, we face a choice of a clearly ethical nature: to preserve the effectiveness of these therapies by perpetuating crazy theories, or to seek the truth at the risk of robbing some patients of their favourite therapeutic resources.