5.2 How can we have confidence in our inferences

I won’t profess to have demonstrated in any conclusive way that an external world exists. Like all interesting philosophical problems, it defies proof – if it were provable, then it would cease to be an issue at all and there would be no reason to continue writing about it. Many of the world’s greatest thinkers have lived and died without resolving the question. I have given many examples of where they stood on this issue. But it does seem reasonable to assert that only if there is something in the world besides our individual minds does it become worthwhile to try to discover what it is and how it works. The drive to learn about the world is more important to those who advance the body of science than any philosophical issues related to the meaning of that activity.

I will develop the rest of this presentation assuming that there is an external world that exists when we are not around to observe it. Given that, this section discusses if and how can we draw reasonable inferences about that world from our experiences of it. This section defines some of the postulates and assumptions that must be accepted to make it possible for people to operate in the world, and for scientists to learn about the world. They are not based on faith, but on a mixture of evidence and reason: carefully crafting theories, gathering evidence, collecting consistent support from countless observations, and a generous application common sense.

As Bertrand Russell wrote, "the general principles of science are believed because mankind have found innumerable instances of their truth and no instances of their falsehood. But this affords no evidence for their truth in the future, unless the inductive principle is assumed." This great man was unable to arrive at a conclusive,deductive proof of induction. But his contributions to the analysis of the problem, and the contributions of many other famous individuals make interesting reading.

John Worrall, a professor of philosophy of science at the London School of Economics wrote:

Nothing in science is going to compel the adoption of a realist attitude towards theories. But this leaves open the possibility that some form of scientific realism, while strictly speaking unnecessary, is nonetheless the most reasonable position to adopt.