In this chapter we will offer some general remarks on the nature of scientific theories - a reasonable beginning to a book bearing the present title. Then we shall say a little about the role of new techniques in the discovery process and subsequent theorizing.
Much has been written about the nature of scientific theories. Perhaps the best-known writer in this field is Karl Popper (1902-1994). Popper argued that no scientific theory can be proved to be correct; it can only be shown to be wrong, or at least flawed. It is the job of scientists to find ways of challenging theories by empirical means. This is only possible if theories are designed to be open to empirical validation - they must be falsifiable. That the moon is made of green cheese is a silly theory (or hypothesis), but it is at least falsifiable: we can go there and check. In contrast, Freud's psychoanalytic theory is not silly, but many have doubted whether, for example, his concept of the Oedipus complex could ever be falsified by empirical observation.
Popper (1959) demonstrates how the process of empirical testing leads to an evolution of theories whereby earlier theories become corrected and often embedded within newer, more inclusive ones. Thus, Newton's theory can still be used in many contemporary situations, such as sending a rocket to the moon. But it was the presence of certain weaknesses in the theory (facts it could not explain) that led to Einstein's theory of relativity - which includes Newton's laws as special cases.
It is now generally agreed that when Popper made his assertions he was thinking about what can be called 'great theories'. Examples are Newton's laws, Darwin's theory of evolution, relativity theory and, most recently, the quantum electrodynamic theory of light. There is no need to write at length about these theories. However, here are a few examples of their power.
Newton's formula, G = (m1 × m2)/d2, where G = gravitational force, m1 and m2 are the masses of two bodies and d2 is the square of the distance between them, has been described by the distinguished physicist Richard Feynman as the most powerful equation of all time (Feynman, 1999): it can