Thoughts in a Haystack

If we accept the idea that science really does give us some sort of knowledge then we must examine what scientific theories tell us about how the world is, and decide what is the scope of scientific knowledge. The modern scientific picture of the world seems to tell us a great deal, not just about how things are now, but how they were millions and even billions of years ago. Astrophysics tells us about the formation of the Earth, the solar system and even the universe, geophysics tells us about the development of mountains, continents and oceans, and biochemistry and evolutionary biology tell us about the development of life itself. Such scientific theories tell us more about familiar things, so, for example, we may learn where a particular river used to flow or how bees pollinate flowers. However, scientific theories, especially those in physics and chemistry, also describe entities that are not part of our everyday experience, such as molecules, atoms, electromagnetic waves, black holes, and so on. Such theories raise particular problems and questions in the philosophy of science; for example, should we believe in the existence of such esoteric and unobservable entities, and if so, what is to count as evidence for their existence and how do we manage to refer to them?

Of course, science does not just describe the world; it also gives us explanations of how and why things are as they are. Often this involves describing unobservable causes of things we observe. Hence, Newton is not famous for discovering that unsupported objects fall to the Earth, he is famous for explaining why they do so (the gravitational force is what causes apples to fall out of trees), and for giving us a law that allows us to calculate the rate at which they do so. Newton's mechanics, like many scientific theories, is formulated in terms of a few fundamental principles or laws. Central to our understanding of science is this idea of laws of nature; for example, it is supposed to be a law of nature that all metals expand when heated. So science seems to tell us about the ultimate nature of things, what the world is made of and how it works. It has even been thought that science has replaced metaphysics not just by telling us about what exists, and explaining what happens in terms of laws of nature and causation, but also by answering other fundamental philosophical questions about, say, the nature of space and time. But what exactly is a law of nature, and what does it mean to say that something has caused something else? What is it to explain something?

Many philosophers and scientists take it for granted that the aim of science is not merely to describe what we see, but also to arrive at the truth about the unobservable entities, laws and causes that lie behind the phenomena we observe. On the other hand, there is also a long tradition of disregarding questions about the real nature of things, the laws of nature and so on, and emphasising instead the search for theories that accurately predict what can be observed, without worrying about whether they are true or false beyond that. The question ... is, 'ought we to believe in the unobservable entities postulated by our best scientific theories?', or more crudely, 'do electrons really exist?'.

- James Ladyman, Understanding the Philosophy of Science