Chance (philosophy)

Indeterminism is the concept that (certain events, or events of certain types) are not caused, or not caused deterministically (cf. causality) by prior events. It is the opposite of determinism and related to chance. It is highly relevant to the philosophical problem of free will, particularly in the form of metaphysical libertarianism.

In science, most specifically quantum theory in physics, indeterminism is the belief that no event is certain and the entire outcome of anything is probabilistic. The Heisenberg uncertainty relations and the "Born rule", proposed by Max Born, are often starting points in support of the indeterministic nature of the universe. Indeterminism is also asserted by Sir Arthur Eddington, and Murray Gell-Mann. Indeterminism has been promoted by the French biologist Jacques Monod's essay "Chance and Necessity". The physicist-chemist Ilya Prigogine argued for indeterminism in complex systems.

Indeterminists do not have to deny that causes exist. Instead, they can maintain that the only causes that exist are of a type that do not constrain the future to a single course; for instance, they can maintain that only necessary and not sufficient causes exist. The necessary/sufficient distinction works as follows:

If x is a necessary cause of y; then the presence of y necessarily implies that x preceded it. The presence of x, however, does not imply that y will occur.

If x is a sufficient cause of y, then the presence of x necessarily implies the presence of y. (However, another cause z may alternatively cause y. Thus the presence of y does not imply the presence of x.)

As Daniel Dennett points out in Freedom Evolves, it is possible for everything to have a necessary cause, even while indeterminism holds and the future is open, because a necessary condition does not lead to a single inevitable effect. Thus "everything has a cause" is, in his opinion, not a clear statement of determinism. Still, a question might arise why this and not that effect occurred: as long as a cause (something in the past) determines the answer to the question "effect A or B" (or why A or B), determinism will hold. On this basis "everything has a cause" might still be understood as an expression of determinism.

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