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Worldviews, by Richard Dewitt Amazing Pic Chapter 8: Instrumentalism and Realism We usually speak of the advancement of knowledge and understanding as the fundamental goals of science, but just as the bottom line in business is increasing profit, the bottom line in science is increasing predictive success. When a scientific theory repeatedly makes impressively precise and accurate predictions, especially with respect to previously unpredictable phenomena, it gets noticed. And at that point it seems reasonable to ask why it is so successful in this regard, where other theories have failed. More precisely, if T1 and T2 are alternative theories regarding the same range of phenomena, and T1 makes consistently better predictions about these phenomena than T2, then it seems like there has to be a reason for this, and the most obvious and plausible reason is that T1 is a truer, more accurate representation of reality than T2. Philosophers who think this way are called realists. Realists believe that the most fundamental aim of a scientific theory is to provide an accurate model of reality, and moreover that the best explanation of the fact that a theory achieves this kind of accuracy is that the theory is true. So those who subscribe to a realist interpretation of the theory of the atom, for example, believe that there really are, atoms which themselves really are made of various types of charged subatomic particles. (Similarly, people who subscribe to a realist interpretation of mathematics believe that numbers are just as real as atoms. And people who subscribe to a realist interpretation of morality believe that moral properties like good and evil are just as real as numbers and atoms.) So why wouldn’t someone be a realist about atoms? The answer lies in the empiricist tradition of science. For centuries scientists agreed that scientific knowledge concerned only that which was, in principle at least, observable. This was a good thing in that it meant that spooks could not be invoked to explain eclipses, comets, bad weather, disease, etc. (Of course most scientists of the 16th-19th centuries believed in spooks, they just didn’t allow them into scientific explanations.) The problem with this very hard line empiricism is that it makes it impossible to acknowledge the existence of very small things, and very far away things, since very small and far away things can’t be observed with the naked eye. Telescopes and microscopes eventually softened this attitude to some degree, but scientists eventually found themselves explaining the results of various experiments by positing the existence of entities that were in principle unobservable. No one has ever seen, or ever will see an atom. Rather, scientists posit their existence to explain a range of phenomena that can be observed. An instrumentalist, then, is someone who typically adheres to a hard line empiricism, granting reality only to things the can actually be observed. The instrumentalist accepts scientific theories involving unobservable entities as useful predictive instruments, but she remains agnostic with respect to the question why they are useful predictive instruments. Philosophers of science will usually identify themselves as being realists or instrumentalists with respect to scientific theories generally. However, within science most theories are at least candidates for realistic interpretation. Your author points out that within science itself theory acceptance goes through an instrumental stage before being considered a candidate for realistic interpretation. The Ptolemaic system. The ancient astronomer Ptolemy (150 A.D.) defended the geocentric conception of the universe against the apparent violation of Plato’s dictum. Years of careful observations had demonstrated unequivocally that the planets did not appear to be moving in uniform circular orbits, which is what Plato’s dictum required. Rather, they would occasionally and regularly start moving backwards. (It’s interesting to ask for the basis of this dictum, and the answer seems to be mainly aesthetic. Circular motion represented a standard of perfection and beauty.) Ptolemy solved that problem by posing a model that preserved the circular motion, by creating epicyles. Retrograde Motion