Clarifies these two concepts that figure so prominently not only in discussions of free will but also in theories of scientific explanation. The question of the status of scientific explanation in an indeterministic world arises repeatedly in subsequent chapters of this book. Even if we do not yet have the final word on the truth or falsity of indeterminism, we need to take account of its possibility in framing philosophical theories of scientific explanations. This essay presents the “received philosophical opinion” on determinism, criticized by John Earman as confused and mistaken, and suggests ways to correct the most egregious errors of the received view.
As Schrödinger observed in one of his essays in 1932, there was an attempt in the beginning to overcome "practical" determinism and only later did we came to admit that such determinism was only theoretical. The opinion previously held was: if we knew exactly the initial velocity and position of every molecule, and we had the time to keep track of all the collisions, it would be possible to predict exactly every thing that happens. Only the practical impossibility: a) of determining exactly the initial conditions of the molecules, and b) of keeping track of all single molecular events, has led to the introduction of "average laws," which were deemed satisfactory because they involved quantities which can really be observed with the senses, and because such laws do not have enough precision to allow us to make sufficiently certain predictions. Therefore, it was thought that phenomena were determined in a strictly causal way, as if the atoms and molecules were considered individually. This formed the foundation of statistical laws, which are the only ones accessible to experience. As pointed out by Schrödinger, the majority of physicists held that a strictly deterministic theoretical framework was indispensable for the description of the physical world. They were convinced that an indeterministic universe was not even "conceivable." They admitted that, at least in an elementary process such as the collision of two atoms, the "final result" is implicitly contained with complete certainty and full precision in the initial conditions. It used to be said in the past, and still is sometimes even today, that an exact natural science is not possible if based on premises other than these; and that without a strictly deterministic premise, science would be completely inconsistent. Our "image" of nature would degenerate into chaos and would therefore not correspond to a vision in which nature actually "exists", since, when all is said and done, nature is not complete chaos. All of this is undoubtedly "false." It is without doubt permitted to modify the picture in the kinetic theory of gases of what happens in nature: one may think that in the collision of two molecules, the trajectory is not determined by the "known laws of collisions," but by an appropriate "role of dice"(cf. Schrödinger, 1932).