High-profile critics of science, from the left and the right sides of the political spectrum, often claim that science is just another form of faith - no different from any religion. Scientists, these critics say, have faith in the belief that science explains everything. The name attached to this supposed faith is 'scientism', which rhymes with Catholicism and Buddhism.

The first problem with this critique of science is the failure to distinguish between the discipline of science itself, and those who claim to be scientists. Self-identified scientists are as diverse as priests - some adhere to the generally defined rules of their discipline, while others may be charlatans, or paedophiles. But in contrast to some of its practitioners, the discipline of science is as far removed from faith as anything can possibly be. Indeed, science can rightly be called the anti-faith discipline.

Although scientific theories are usually constructed to explain previously unexplained results, they are only meaningful if they lead to empirical predictions of future events, or properties of the natural world that are not otherwise anticipated. Isaac Newton's laws of motion and gravity predict the dates of irregular lunar eclipses, which would otherwise be unexpected. Newton's laws are also used today, to predict an extraordinary number of ordinary daily events.

Theories that provide more accurate predictions and interpretations of the natural world eventually win, in the intellectual marketplace of scientific ideas. Sometimes, well-established theories - like Newton's - are superseded, not because they are fundamentally wrong, but because they express an approximation of the natural world that is later refined or generalised. So Albert Einstein's theories of relativity incorporate and go beyond Newton's laws, yet it is clear to physicists that these theories still do not represent the final word. When predictions do not pan out, an honest scientist must be ready to discard or modify their theory, no matter how dear the theory may be to their heart.

Steadfast belief in the truth of a proposition that is not supported by scientific theory or evidence - or, indeed, in the truth of a proposition that flies in the face of empirical evidence - is the definition of faith. Good science is an enemy of faith, and faith is an enemy of good science.

Don't get me wrong - I am a scientist with hopes and dreams. But I do not hold 'faith' in anything. Instead, I view the future in terms of probabilities. The Sun has come up every morning of my life, and I have every reason to think it will do so for the rest of my days. There is, however, a slight chance that I am wrong. I think my friends will come to my aid, if I need them in future, but again I might be wrong. Science and hope are different from scientism or faith.

Academic critics of science, as a discipline, are mostly irrelevant today. Instead, society is faced with covert religionists and spiritualists, who distort science and manipulate its language, to convince the public at large of the truth of their faith-based claims.

In the USA, the Catholic and Protestant fundamentalists who dominate George W Bush's national bioethics commission claim that 'scientific evidence' proves a newly fertilised embryo is a human being. As a result, these fundamentalists claim, human beings are murdered in the derivation of embryonic stem cells. In Western Europe, scientific theories and empirical data are routinely misrepresented or ignored by organic food enthusiasts, who hold steadfast to a faith in the goodness of Mother Nature and the danger of biotechnology.

What is the solution, for advancing human and environmental health and wellbeing in today's world? A direct attack on faith will almost certainly fail, because faith is the instinctive norm for our species. The possibility that faith will ever be dislodged is extremely low. The answer, I believe, is the one proposed by Robert May, outgoing president of the Royal Society: 'Consult widely, embrace dissent, engage people even if they don't come forward voluntarily who are likely to disagree with you, expose the argument and expose uncertainty.' This is our only hope.

Lee Silver is author of books including Remaking Eden: Cloning, Genetic Engineering and the Future of Humankind? (buy this book from Amazon (UK) or Amazon (USA)), and Mouse Genetics: Concepts and Applications (buy this book from Amazon (UK) or Amazon (USA)). See his website.