indeterministic

Indeterministic describes a characteristic of processes or events whose outcomes are not fixed by prior states. The notion may reflect intrinsic indeterminacy in nature, or limits of knowledge. It is used in philosophy, physics, and systems theory to contrast determinism—where a complete set of initial conditions logically fixes all future states—with situations in which predictions cannot be made with certainty even with perfect information about the present.

In physics, indeterminism is most often associated with quantum mechanics, where measurement outcomes are inherently probabilistic. The wavefunction assigns probabilities, and individual events such as a particular decay or a photon’s detection cannot be predicted with certainty. Some interpretations posit hidden variables; others embrace intrinsic randomness. Classical systems can also appear indeterministic when they are highly sensitive to initial conditions, as in chaotic dynamics, where long-term prediction is impractical even if the laws are deterministic.

In philosophy, indeterminism is a position arguing that not all events are determined by prior events or laws. This stance is debated in discussions of free will, moral responsibility, and scientific explanations. It is important to distinguish indeterminism from randomness or stochastic models: indeterminism concerns the nature of causation and determinacy, while randomness describes unpredictable outcomes that nevertheless may conform to probabilistic rules.

Related terms include determinism, randomness, and nondeterminism, which are used in different disciplines to describe variations in predictability, causation, and computation.