- Non-determinism redirects here. For similar articles, see Indeterminacy
is the philosophical
belief contradictory to determinism
: that there are events which do not correspond with determinism (and therefore are uncaused in some sense).
- No event is caused at all
- Some events are not caused at all
- Some events are partially caused
- All events are partially caused.
At one time, it was assumed in the physical sciences that if the behavior observed in a system cannot be predicted, the problem is due to lack of fine-grained information, so that a sufficiently detailed investigation would eventually result in a deterministic theory ("If you knew exactly all the forces acting on the dice, you would be able to predict which number comes up"). However, the advent of quantum mechanics
removed the underpinning from that approach, with the claim that (at least according to the Copenhagen interpretation
) the most basic constituents of matter behave indeterministically
, in accordance with such properties as the uncertainty principle
Quantum indeterminism was controversial on its introduction, with Einstein
among the opposition, but gradually gained ground. Experiments confirmed the correctness of quantum mechanics, with a test of the Bell's theorem
by Alain Aspect
being particularly important because it showed that determinism and locality
cannot both be true. Bohmian quantum mechanics
remains the main attempt to preserve determinism (albeit at the expense of locality).
Types of cause
Causes are often distinguished into two types: Necessary and sufficient.
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 cause does not lead to a single inevitable effect. Thus "everything (does not) have a cause" is not a clear statement of (in)determinism.
One of the important philosophical implications of determinsim is that, according to incompatibilists, it undermines many versions of free will
. Correspondingly, believers in free will
often appeal to physical indeterminism. (See compatibilism
for a third option.)