It is sometimes said that one of the casualties of the general suspicion and mistrust that permeated the old Soviet Union was that the distinction between truth and other motivations to believe tended to break down. Upon hearing a purported piece of information, the reaction was not 'Is this true?' but 'Why is this person saying this? - What machinations or manipulations are going on here?' The question of truth did not, as it were, have the social space in which it could breath.

The absolutist lays down the law, but the relativist hears only roaring and bawling. Or, when the relativist voice, as it is heard from philosophers such as Nietzsche or James, itself starts to grate and sounds shrill, as it often does, and when the relativist then offers concessions, the absolutist hears only insincerity. The war of words can often turn into a dialogue of the deaf, and this too if part of its power to arouse outrage and fury.

There may be rhetoric about the socially constructed nature of Western science, but wherever it matters, there is no alternative. There are no specifically Hindu or Taoist designs for mobile phones, faxes or televisions. There are no satellites based on feminist alternatives to quantum theory. Even that great public sceptic about the value of science, Prince Charles, never flies a helicopter burning homeopathically diluted petrol, that is, water with only a memory of benzine molecules, maintained by a schedule derived from reading tea leaves, and navigated by a crystal ball.

Chance is as relentless as necessity.

People who have cut their teeth on philosophical problems of rationality, knowledge, perception, free will and other minds are well placed to think better about problems of evidence, decision making, responsibility and ethics that life throws up.

There are normal times when it is wholly admirable to be steadfast, resolute, unconflicted, and therefore when integrity is unmistakenly a virtue. The person of integrity knows what to do, and does it. But as we have been exploring, there are also times when certainty and single-mindedness indicate something less admirable: a deafness to voices that should be heard or a blindness to aspects of a situation that need to be considered.

This doctrine, that of the ghost in the machine, strictly separates the mind or soul from the body. And by doing so it takes the soul outside the sphere of mechanical or scientific explanation. It splits the world of the mind from the world of science. It is often supposed to protect our cherished free will.