Mechanistic Determinism

Mechanistic determinism is the 19th-century scientific worldview that The Faith of a Scientist repeatedly sets against quantum uncertainty and free agency. Henry Eyring describes it as the view that “if one were given the state of the universe at any instant of time, a sufficiently expert mathematician could calculate the state of things at all times to come.” Its emblem in the book is La Place’s reply to Napoleon’s question about God: “Sire, I have no need of that hypothesis.”

Eyring’s argument is that this clockwork picture “left no place for the great religious principle of free will” — and that 20th-century physics undid it. “Then quantum mechanics brought with it the uncertainty principle. This principle eliminates the possibility of predicting the future exactly, and tends to confirm that fundamental Christian tenet that man enjoys free agency as a divine gift.” He frames “our century” as “a turning away from the mechanistic determinism of the 19th Century,” calling the uncertainty principle “a humbler approach to the mysteries of creation.” The concept is thus the foil for the book’s reconciliation of science with Free Will and Agency.

Context: Mechanistic (or Laplacian) determinism is the classical-physics view, epitomized by Laplace’s “demon,” that the universe’s entire future is fixed by its present state and Newton’s laws — a position widely held to have been complicated by quantum mechanics in the 20th century.

Where this appears

• The Faith of a Scientist — the 19th-century clockwork worldview Eyring contrasts with the quantum uncertainty principle, which he reads as restoring room for free agency.