G Reductionism
Nature exists on an immense range of physical scales and degrees of complexity. Reductionism is the doctrine that sciences of complex systems rest on sciences of simpler systems.
Psychology rests on biology, which rests on chemistry, which rests on physics. The scientist’s naive view that the world is made up of entities and processes that are within the realm of physics is sometimes called physi- calism. Physicalism is a tame form of reductionism, little more than saying that there are no supernatural causes or effects in science.A strong form of reductionism says that everything will eventually be explained by physics alone. Probably very few scientists, and no philosophers, buy into this version. The philosopher Daniel Dennett calls the tame form “weak reductionism” and the extreme form “greedy” reductionionism.28 The limit of greedy reductionism is determinism (or causal determinism since, of course, there are many kinds of determinism), which is the concept that, if we knew everything about all of the particles and forces everywhere in the universe, then we could use a super-duper computer to predict all past and future events. Weak reductionism denies that we’ll be able to fully explain the complex aspects of nature in terms of the simple ones.
The physicist’s grail of a “Theory of Everything”29 (ToE) illustrates the distinction: ToE is the catchy name given to the hoped-for theory that will unite the major known forces of nature; namely, gravity, electromagnetism, and the strong and weak forces at play in the nucleus of the atom. If it could be constructed, a ToE would represent an amazing intellectual feat, but it will not explain, literally, everything. A ToE would explain the basic forces, fields, and particles in the universe; detailed quantitative descriptions of their properties and interactions; and, no doubt, jaw-dropping explanations of phenomena right out of science fiction—“time-travel!,” “worm-holes!” Yet, although people and oil paints do obey the laws of physics, a ToE will not be able to predict the existence of either people or oil paints, let alone how a portrait will look before the artist paints it. There will always be far more things left unexplained than explained by physical theories.
Reductionism cannot mean that all sciences are ultimately derivable from a more basic science. This raises another question, however. If strong reductionism is invalid, then how should we think about the relationships among the different levels of analysis of science?
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