Path Integral (Feynman)

The path integral is Richard Feynman's reformulation of quantum mechanics, in which a particle traveling from point A to point B does not take one path. It takes every possible path simultaneously, including paths through solid walls, paths that loop around the moon, paths that violate ordinary causality. Each path contributes a complex amplitude to the final probability of the particle's arrival.

The reason particles behave “sensibly” is that the contributions from most paths cancel each other out through destructive interference. The wall does not block the particle by stopping it; the wall ensures that the amplitudes for paths-through-the-wall sum to nearly zero.

What this gives the framework is the precise mathematical form of subtractive manifestation. The manifest behavior of any physical system is the residue of cancellation across an infinite field of possibilities. Reality is not built up from nothing. It is what remains after everything else has been subtracted.

The path integral is, in physics' own vocabulary, a doctrine that mystics across continents have asserted for three thousand years.