The Stochastic Turn

Physics was deterministic. Given initial conditions and laws of motion, the future was determined. Laplace’s demon, knowing every particle’s position and velocity, could compute all past and future states. Probability entered as a tool for managing ignorance — statistical mechanics used probabilities not because nature was random but because the observer lacked complete information.

The transition to fundamental stochasticity was not a single event but a gradual infiltration across multiple subfields. Radioactive decay introduced irreducible randomness in nuclear physics. Quantum mechanics made measurement outcomes probabilistic in principle. Chaos theory showed that deterministic systems could produce effectively random behavior. Stochastic processes entered fluid mechanics through turbulence, biology through genetics, and cosmology through the quantum origin of structure.

The paper traces this infiltration and identifies that the shift was not uniform. Different fields adopted stochasticity at different times, for different reasons, and with different philosophical attitudes. Nuclear physicists accepted fundamental randomness early. Fluid dynamicists resisted longer, treating randomness as a practical convenience. Cosmologists came last, because deterministic equations had been spectacularly successful.

The structural point: the rise of stochasticity in physics was not a revolution — no paradigm shifted overnight. It was a slow conceptual erosion where determinism retreated field by field, each retreat justified differently. The result is a physics where probability is fundamental in some domains and merely practical in others, and the boundary between fundamental and practical randomness remains unresolved.