Generally speaking, the realist position is the belief that everything that exists has a 'self', an intrinsic nature, which scientific method, over the decades and centuries, is capable of cataloging in a way that is both correct and exact. The Universe exists in a way that is just exactly so, and by carefully sifting the evidence we get from asking the right questions humans can discover that absolute nature. Instrumentalism, on the other hand, holds that scientific theories and models of the universe are valid only in the sense that they are useful in predicting events and explaining data consistently, while at the same time making no claim that anything they describe actually exists.
To illustrate these positions, we can again use our particles as a base. The Cartesian model said that the world is made of particles of matter, whose behavior was described in classical terms of collisions like the ones that we see on our scale. As research exposed more of the microworld, physicists continued to describe it in visual terms that had analogues in the macroworld. When the electron was first introduced into the theories, the two main atomic models were the Plum Pudding (electrons embedded in the nucleus) and the Planetary (electrons orbiting the nucleus) models. The effect of the quantum revolution was to force the experts to admit that there was no longer any way to visualize the electron wave/particle by analogy to anything on our scale. (26) To relate what they considered to be the reality of the electron, all they could use was mathematical description.
Here, an instrumentalist could enter and explain that we can never do more than 'save the appearances'. One should develop a hypothesis that 'doesn't contradict the world', explain the data neatly and cleverly, but don't expect to describe ontological reality. The realist may retort that the mathematical description is valid as the 'visualization' of the atom - in fact, it is really the most accurate model. Stemming back to the days of Pythagoras, who maintained that numbers were reality itself, western thought has tended to accord mathematics special status as axiomatic truth. However, developments such as non-Euclidian geometry in the last century, as well as Karl Godel's incompleteness theorem of the 1930's, have made it difficult to rely on the axioms of math for absolute proof of anything other than statements made within the framework of the math itself. In fact, says Wallace's instrumentalist, mathematical truths are just as conventional as the laws of physics we use math to describe. These things are handy as experience filters, but they have no reference to physical fact. Theories of subatomic particles can be as logically self-consistent as you like, but the whole scheme is entirely arbitrary.
Wallace contends that when discussing the pre-rational assumptions of realism, most working scientists and mathematicians admit to the relative nature of their work. However, in practice and in education, the metaphysical assumption of absolute existence from the mechanical worldview is rarely considered, much less challenged. In spite of the quantum and relativity revolutions, contemporary physical sciences have not shed the legacy of Newtonian ontology and ancient Greek reasoning.
Copyright © 2005 Dan Haig