Conclusion

In this chapter, we have seen how philosophers have approached some of the central questions about science. What is a theory? How do we explain the events that happen in our world? How do we jus­tify scientific claims? What is a law of nature? And, finally, what do we mean when we say that A causes B? Of course, there are many important questions in the philosophy of science that I have not dis­cussed, and starting from the work we have done in this chapter, you can go on to look at some of these questions.

Whichever questions you choose to follow up, you will find again and again, as we have seen once more in this chapter, that questions in one area of philosophy impinge on another.

But I want to end this chapter by making a point about the con­tinuity not just between different parts of philosophy, but between philosophy and science. To make this point, I need to say a little more about causation.

Causation is important, in part, because the kind of understand­ing science offers us is an understanding of the causes of events in our universe. To know what caused an event is to know why it hap­pened, and that is to understand the event. Indeed, it has been sug­gested that what it means to understand an event scientifically is to understand its causes. Many philosophers of science up to our own century held that every event had its causes and that the task of sci­ence was to find out what they were. The thesis that every event is caused is called “determinism.” If determinism is true, then once the universe started, everything that happened afterward was deter­mined by natural laws.

But scientists have argued in this century that determinism is not true. Quantum theory, which is the theory that most physicists now believe, says that there are some events that do not have causes. (I'll say a little more about this in 9.10.) The theory says what the prob­ability is at any time of certain events—such as the emission of a particle by a radioactive substance. But it often does not say why any particular particle is emitted when it is. (And string theory, which is the current major candidate to succeed quantum theory, agrees with quantum theory here.) If understanding an event scientifically means knowing what caused it, then this means that scientists believe they have scientific evidence that some things cannot be sci­entifically understood! Thus quantum theory denies the philosoph­ical thesis that reality can be fully understood; and it rejects the philosophical principle of sufficient reason, which goes back to classical Greek philosophy and says that every event has a cause. It does look as though, just as we cannot isolate one branch of philos­ophy from the others, so we cannot isolate philosophy from our sci­entific beliefs.

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