Philosophy is primarily about method; it’s about the principles that tell us how to discover knowledge. And even a quick look at the history of science shows us that these principles are not obvious. In astronomy, for instance, Ptolemy and Copernicus did not simply disagree in their scientific conclusions about the solar system; they also disagreed in their underlying philosophic ideas about how to develop a theory of the solar system. In essence, Ptolemy thought it was best to settle for a mathematical description of the appearances, whereas Copernicus began the transition to focusing on causal explanations. So what is the goal of science–to describe appearances, or to identify causes? The answer depends on the philosophy you accept.
Similarly, in 17th century physics, Descartes and Newton did not simply disagree in their scientific theories; they strongly disagreed about the basic method of developing such theories. Descartes wanted to deduce physics from axioms, whereas Newton induced his laws from observational evidence. So what is the essential nature of scientific method–is it primarily deductive, or primarily inductive? And what is the role of experiment in science? The answers depend on your theory of knowledge.
Here’s another example: Consider the contrast between Lavoisier, the father of modern chemistry, and the alchemists of the previous era. Lavoisier did not merely reject the scientific conclusions of the alchemists; he rejected their method of concept-formation and he originated a new chemical language, and then he used a quantitative method for establishing causal relationships among his concepts. So how do we form valid concepts, and what is the proper role of mathematics in physical science? Again, your answers to such fundamental questions will depend on the philosophy you accept.
Finally, consider the battle between two late 19th century physicists, Boltzmann and Mach. Boltzmann was the leading advocate of the atomic theory and he used that theory to develop the field of statistical thermodynamics. Mach, on the other hand, was a leading advocate of positivism; he thought that physicists should stick to what they can see, and that the atomic theory was nothing more than speculative metaphysics. So what is the relationship between observation and theory, and how is a theory proven, and are there limits to scientific knowledge? Once again, these are philosophic questions.
Such issues have not gone away with time. There is a great deal of controversy in theoretical physics today, and these basic issues of method are at the heart of the controversy. Some physicists say that string theory is a major triumph that has unified quantum mechanics and relativity theory for the first time. Other physicists argue that string theory is just a mathematical game detached from reality–that it isn’t a theory of everything, but instead a theory of anything. And we’re starting to hear similar criticisms of Big Bang cosmology; if the theory is so flexible that it can explain anything, the critics say, perhaps it actually explains nothing.
How do we decide these issues? How do we know the right method of doing science, and what standards should we use to evaluate scientific ideas? These are some of the questions that I try to answer in my book. . . .