Fact or Opinion?

Science is very impressive. We all benefit from its successes. I wouldn't be writing this book if the advances in medicine hadn't provided a means for me to survive a serious illness that struck twenty years ago. When I type up my scribblings, I use all the electronic wizardry of a sophisticated word processor. We all enjoy, every day of our lives, the new things made possible by the advance of science.

Science also enlightens our minds and enlarges our imaginations. We know that we are the inhabitants of an unremarkable planet, circling an unremarkable star, in a universe that contains at least ten thousand million million million stars. Once this universe looked very different from the way it does today, and it has had a long history, going back fourteen billion years to the fiery explosion of the Big Bang that gave it birth. Science tells us what makes the stars shine, why water is wet, how genetic information is conveyed from one generation to the next. It's a story of astonishing achievement, and perhaps the most impressive thing about it is that we can all agree on the answers it provides. The dust really does settle. Not only does science answer questions, it does so to universal satisfaction.

It would be foolish to deny that there's a striking contrast with religion. We'll not all agree on the answer to the most fundamental religious question of them all: "Is there a God?" Although the different faiths clearly refer to a common human experience of the spiritual, they seem to say such different things about it. Is the individual human self of unique value and significance (so say Judaism, Christianity, and Islam), is it, in fact, an illusion (so says Buddhism), or is it recycled through reincarnation (so says Hinduism)? Is suffering something to be accepted or avoided? And so on.

The conclusion seems clear. Science is based on facts and leads to real knowledge. Religion is just based on opinion. It may help you or me to live our lives — religion may be "true for me" or "true for you" — but it's not just plain "true," pure and simple. So it may seem, but I believe that such a conclusion would be a fundamental mistake of the most disastrous kind. If I thought it were true, I would not be a religious person. How could something really help one in one's life if it were just a personal illusion? Only the true can be a real basis for living — and facing death.

Two mistakes lead to the false conclusion that science and religion involve the encounter of fact with mere opinion. One is a mistake about science. The other is a mistake about religion. Let's take science first.

Many people's impression of how science progresses is that a prediction is made ("adding factor X will turn the liquid green"), an experiment is performed (it does turn green), and a great new discovery has been made. In actual fact, it is all a good deal more subtle and more interesting than that. In the first case, the facts that concern scientists are already interpreted facts. Most of the time you can't see directly what's happening. You have to infer it from the things you can see, and that inference requires the use of theoretical interpretation.

It's quite hard to give an example of this for the nonscientist because modern apparatus is so complicated and technical, exactly illustrating my point that you have to know the theory in order to understand the experiment. Rather than a "gee-whizz" discussion of electronic gadgetry, let me show you a picture. It's meant to represent a photograph of tracks in a device widely used for many years in my old subject of elementary particle physics (the study of the smallest bits of matter). The apparatus is called a bubble chamber. It contains a liquid that is just about to boil. A particle passing through triggers a chain of little bubbles, which make its path visible. It's a bit like bubbles rising in a glass of beer, and, in fact, the man who invented the device is said to have got the idea while brooding on his lunchtime drink. A photograph of a bubble chamber will show lots of these tracks, a complicated pattern of curls and swirls. Figure 1 on the following page is a simplified example of this.

Doubtless we could all painstakingly follow each track and agree on what sort of shape it had, but this, by itself, would be of no scientific interest whatsoever. The patterns only become significant when they're interpreted as indicating such-and-such a particle moving with such-and-such a speed and being made to curl around by the strong magnetic field applied to the chamber. Then it all becomes meaningful and interesting. I remember once being shown a particular photograph that, when its significance was explained by the experimentalists, turned out to show the existence of an entirely new particle. This was really exciting. Without the interpretation, it was just a mess.

Now the problem is this. In order to make the interpretation, you have to know some science already. You can't just stare at the world; you have to view it from a chosen point of view. Choosing the point of view involves an act of intellectual daring in betting that things might be this way. This means that in science, experiment and theory, fact and interpretation, are always mixed up with each other. They're as inseparable as the meaning and the ink that together make up the words of this book. Someone once said that scientists wear "spectacles behind the eyes" — it's not just what they see but the way that they see it that counts. In other words, science uses a mixture of fact and opinion. Of course there are reasons for the opinions, and opinions can be revised when they don't seem to work very well, but you can't do without them.

There's another reason why this is so that I haven't mentioned so far. In a bubble chamber photograph, there are likely to be some tracks that have nothing to do with the experiment, but are accidental strays, coming, perhaps, from the cosmic rays that continually bombard the Earth from outer space (in my figure, this is probably what the horizontal lines are, the really significant bit being the V at the bottom). In order to interpret what is happening correctly, it is necessary to identify and eliminate these spurious contributions. In the trade, this is called the problem of the "background." There is no rule book you can consult to tell you how to strain out these unwanted additional effects. It's a matter of judgement, and so, ultimately, of informed opinion, that this has been accomplished successfully. I could tell you some horror stories of incorrect conclusions that were reached because of errors made about background effects.

The idea that strange effects may be due to unexpected background can also lead to splendid successes. When the planet Uranus was discovered in the eighteenth century, astronomers found that it was not moving through the heavens in the way that Newton's theory of gravity predicted, but his theory was far too...