“What is Truth? said jesting Pilate; and would not wait for an answer.” Francis Bacon’s well known quotation shows Pilate to be a busy and sensible administrator, who was aware of problems but who knew how to avoid unnecessary conflict most of the time. However, his washing of hands for the trial of Jesus had unexpected consequences. He realized that any discussion of truth awakens arguments, since people tend to select their facts to support their view.

But what is truth in science? Should this not be easier to establish and be more clear cut, since facts can be tested and proved by replication? One would like to think so, and it is this issue that Roger Newton, an emeritus professor of physics at Indiana University in the US, addresses in this book. One of the first questions he asks is whether science differs from other activities. This is a key theme of the so-called “science wars”, in which scientists – particularly physicists – have argued that science is being misinterpreted and devalued by certain sociologists who are known as “Post-modernists” and “Constructivists” (see “What’s wrong with relativism?”).

One of the sociologists is David Bloor of Edinburgh University, who claims that “knowledge for the sociologist is whatever men take to be knowledge”, and that objectivity is nothing more than “institutionalized belief”. But Newton explains that while there is some subjectivity in science, objectivity dominates. He attacks Bloor’s “principle of symmetry”, which “enjoins sociologists to disregard [truth] in the sense of treating both true and false beliefs alike for the purpose of explanation”. Scientists would consider that there is a big difference between true and false – and they are probably too busy to be aware of the harm that is being done by opinions such as Bloor’s.

Looking back through history, one can see that it generally takes a few special people and a favourable society for the idea to emerge that if you have a theory, then you should test it. Indeed, the author makes the interesting suggestion that science is not a natural development in most civilizations. Societies tend to have belief systems, and the thought of trying to prove yourself wrong is not acceptable to most in authority, who might lose power as a result. According to the author, laboratory science as we now know it was developed by Robert Boyle – although for my money it was Galileo who first pointed out that one should test one’s ideas experimentally. The author describes Boyle’s famous argument with Thomas Hobbes, who considered the vacuum to be nothing more than a metaphysical concept. Hobbes felt that experiments were therefore inappropriate and that only rational argument mattered. But when Boyle used a new and better vacuum pump to establish the law that bears his name, one might think that experimental science had at last won the day.

However, the author describes how sociologists like Bloor take examples where ideas and proofs have changed with time to deduce that science is only a conventional system of beliefs established by scientists, and that these beliefs change with time. Newton explains that Bloor fails to understand that as new information becomes available, the old idea often holds good, but the region over which it is valid becomes better defined. For example, Isaac Newton’s laws were not “overthrown” by Einstein’s relativity theory – but were limited to velocities much less than the velocity of light.

The author also discusses the ideas of radical feminists like Sandra Harding, who emphasize personal experience as a source of knowledge and who ignore the question of replication. She considers that as most science has been developed by men it is therefore biased – and has even referred to Newton’s laws as a “rape manual”. It is, of course, useful for scientists to be reminded that others often have very different views of science and that they should be prepared to talk to them. However, such discussions are often surprisingly difficult, and this book should help scientists to have a reasonable public debate.

Other topics that the author looks at include the role of theories and facts – as well as pseudo-facts, such as cold fusion. Newton correctly says that Martin Fleischmann and Stanley Pons’ original work has been extensively tested and is discredited, although I suspect he would be surprised to know that some “true believers” still continue to come up with new and even more fantastic claims. (Some even argue that black spots on photographic plates were created by black holes produced by cold fusion!) The author also emphasizes the great contribution to the question of scientific truth made by the philosopher Karl Popper, who said that a theory cannot be proved, only disproved. A satisfactory theory should be falsifiable, which leads the author on to the question of whether or not psychoanalysis is a science. Newton says that one of the most telling arguments against psychoanalysis as a science “is that its system can easily produce plausible explanations of symptoms or dreams…but there appears to be no way to show that the explanation is wrong”. (This would be a useful argument to employ in cases of “recovered memory”.)

It struck me that the quotation in the book from the philosopher Imre Lakatos that “there is no falsification before the emergence of a better theory” could be applied to the current debate about the value of the relative energy density of the universe, W. The only reasonable theory of the big bang is “inflation”, which proposes that the universe expanded extremely rapidly for a short period after the big bang. Inflation requires W to be exactly one (to four decimal places!), which would mean that the universe will eventually settle down and stop expanding. However, more and more experimental observations suggest that W is about 0.3 ± 0.1, which would mean that the universe will go on expanding forever. Many theorists strongly resist these new results, arguing that there is no theory other than inflation. (Inflation could be salvaged if there were a “cosmological constant” – a large-scale repulsive force that permeated the universe – but many theorists tend to reject this type of constant, even though recent data on supernovae are exciting.)

Einstein is generally considered to be this century’s greatest physicist, but he is rather criticized in this book for appearing to reject probability as the heart of physics, famously saying that he did not believe that “God played dice with the world”. The author describes the Einstein-Podolsky-Rosen (EPR) paradox, in which two particles are produced at a point and then fly off in opposite directions at the speed of light. Quantum mechanics says that one particle must have spin up and the other spin down, but you cannot know which is which until you measure their spin. Einstein was worried about the following question: if you measured the spin of one particle, then how could the other particle know that it must have the opposite sign – given that any signal sent from the first measurement would have to travel faster than light?

Recent experiments to test the EPR paradox have come out in favour of quantum mechanics and have shown Einstein to have taken the wrong approach. It therefore surprised me that Newton says that the results are “still somewhat controversial”. As Andrei Linde explained to me ten years ago, the initial system that produced the two particles has to obey the laws of quantum mechanics, and the fact that parts of this system are moving away with the velocity of light does not change the need for the system to continue to obey these laws. End of paradox, for me at least!

It seems to me that the relative proportions of subjectivity and objectivity in science are crucial for understanding truth. David Bloor considers subjectivity to be the critical factor and to dominate (Physics World March p23). Scientists, however, strive to be completely objective and to eliminate subjective bias before, during and after their work. Nevertheless, there is some element of subjectivity. Evgeny Feinberg gave the following example to me. Suppose a theory is proposed and then experiments are done to test it. After a certain number of experiments that agree with the predictions, people assume the theory to be “proved”. But how many experiments are needed? This is a subjective decision that depends on the nature and quality of the experiments and the experimenters. Thus science has a subjective element, but it is dominantly objective.

So what is the truth of science? The merit of this book is that it explains the complexity of the question. A theory is considered never to be absolutely true, but to be provisional and approximate. Science makes a web or network of understanding, into which known facts can fit. This coherence is central to the recognition of truths. Science forms a basis for action because of the power of prediction. After all, when sociologists are passengers on board a plane, they – like scientists – expect the laws of physics not to change before the plane lands safely. And although quantum theory is taken as the basis of truth, the problem is that explaining its truths can sometimes only be achieved in the language of mathematics. So the nearest that one can come to an answer is that science is a “rationally coherent structure of comprehending the world”, but one needs to study the book to understand the strengths and weaknesses of this partial answer.

The author says that his book is intended for anyone with some scientific education, and that it is not for professional philosophers or sociologists of science. However, I think it would be useful for both groups. It would help the former to widen their horizons, and provide the latter with some professional guidance in language that is not too technical. But would they read it? At a recent meeting between scientists from CERN and philosophers from Geneva University, I showed Newton’s book to a philosopher who specializes in the history of quantum theory. She intends to buy the book – and I hope others like her will do so too.