In her attack on Aids dissenters ("The fanaticism of denial that must be exposed", September 14), Tara Smith skirts over a fundamental problem for scientists, namely how to recognise when the majority view is wrong.

Some years ago I suggested, in these pages, an approach that could help answer this question.

Simply put, if a knowledgeable minority persists in attacking a majority viewpoint then this viewpoint is probably wrong.

In the 1980s, for example, every authoritative voice said that stomach ulcers were caused by stress; a minority view, which eventually prevailed, was that a bacterium was responsible.

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In 1983, Smith would doubtless have railed against Barry Marshall and Robin Warren as "attention seekers" for holding this minority view, which eventually won them a Nobel prize.

If we apply the above "law" to today's scientific problems we can conclude that our views on the following are wrong: evolution, the Big Bang, man-made global warming and, of course, the causation of Aids.

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In contrast, we can accept that influenza is caused by a virus simply because, unlike these other "truths", no knowledgeable minority claims the opposite.

Milton Wainwright
Sheffield