Anscombeの哲学第四課

Newtonの物理学の悪い影響を表します。
Many scholars received the impression that Newtonian laws provide determinism in any system based on the fact that the solar system can be understood by them. However, although planetary movements can be traced both backwards and forwards in time, movements of animals on the Earth's surface cannot. This seems to be due to the fact that the solar system involves inanimate masses and gravity, while on the Earth, forces can be generated, turned on and off, and blocked. Thus, even assuming that there are laws for all forces (thermal, nuclear, etc), what forces are generated when and how they will be responded to may not be known. Given that we know a force is applied, the acceleration will be determined, though.
Anscombe uses the analogy of a simple two-player card game for the solar system. Given the rules of the game and the state of the cards dealt at any time, we can trace backwards to the original deck or forwards to the outcome. The state of the inside of a planet, on the other hand, is like a game of chess. Even if the rules are clearly understood and adhered to, the next moves are seldom uniquely determined.
Anscombe quotes an author discussing how in the cases of a particle's movement, a field under Maxwell's equations, and the planets under Newton's laws, we are able to deduce the past and future states of the systems. This is to illustrate how the success of Newtonian physics in predicting the planetary movements may lull us into considering any system to be deterministic.
However, it may be noted that chess could in fact be deterministic, should anybody be able to generate and assess all moves in the game tree. The number of possibilities at each move would rarely be one, though. However, knowing the psychology, history, and physical state of the players, it could theoretically be possible to predict every move. Thus, the question of whether or not a system is deterministic may be answered differently depending on how much information we have. The same may be true for interactions in nature (cf Hume's essay on Liberty and Necessity).
Anscombe discusses the fact that the statement that the system is deterministic must include any external forces which could enter it at a later time. However, in the case of the solar system, no external forces can exist by the dictates of nature.
The author now discusses necessitating and non-necessitating causes. A necessitating cause C is one after which it is impossible for effect E not to occur unless there is some sort of intervening force. A non-necessitating cause is one after which it is possible for effect E not to occur. An example of this is Feynman's bomb, which is detonated only if a Geiger counter produces a certain reading for a given lump of radioactive material (this is not something which can be determined with certainty, due to the nature of the material used). A necessitating cause might be rabies, which will induce fatality if left untreated.
Max Born defined causality as a dependency relation between effect and cause. The author does not concur with this, as the effect might occur due to some other cause. Different notions of causality seem to be explored in order to shed light on how causality in nature can be compatible with a lack of determinism.
A philosopher named C.D. Broad defined indeterminism as meaning that whatever happened was accidental. The intermediate steps might be causal (e.g. how a Geiger counter moves), but the final outcome was indeterminate. According to Broad, human choices are causal events (lead to effects), but the choices themselves may or may not have been caused.
The next discourse is on two objections between connecting indeterminism in quantum physics with the freedom granted to the will.
The first objection is that ethical behavior cannot be reduced to mere happenstance. Apparently, the reconciliation of physical determinism and ethical freedom has been a concern of philosophy since the days of Kant. The author indicates that such a reconciliation is impossible, saying that the physically determined renders the will impossible, i.e. that if his actions have already been decided, there is no place for his will. Thus, physical indeterminism is necessary for freedom. However, it is insufficient, since freedom involves acting in accord with an idea, and a random physical occurrence does not imply the presence of such an idea.
The second objection is that the will cannot determine what nature leaves undetermined. However, the author asserts that the will could be determining an effect that was not the same effect which could have resulted from another cause (within the bounds of the quantum probability distribution). His example involves the particles in a box which can form various color patterns. If some particles were to constantly spell "Coca-Cola", this may not be realated to the statistical distribution which determines the patterns of the other particles. Thus, there may be no conflict.
Determinism is still adhered to by many who think that, even if only probabilities hold at the microscopic level, the macroscopic outcome is predictable. Feyman's bomb and Geiger counter example overrides the above logic. In fact, quantum physics is not required to make determinism impractical. 決定論が絶対的にありえません。 The fact that the laws of nature guarantee that a certain unique outcome will ensue in a constrained environment without external interference does not imply that nature as a whole is deterministic.
A second mistake of modern philosophy besides determinism is the belief that a singular cause and effect relationship implies a universal cause and effect pattern. Regularities in nature are not a sufficient justification for such a logical transition. It seems to me that the validity of a derivation of universal causality from singular causality would require a deterministic universe. In such a case, any single event could be traced back to a set of core causes. Such a philosophy, though, discounts interference and prevention, which block the instantiation of effects.