Fechner's law

n. The idea that the perceived intensity of a sensation increases as the log of the physical intensity of the stimulus multiplied by a constant for each sense. This implies that perception changes linearly as the stimulus changes geometrically: perceptual intensity = ^*log physical intensity. The constant was supposed to be different for different senses. This was an improvement on Weber's law, which had supposed that increases in sensation increased linearly with stimulus intensity, and has been largely replaced by the power law, which suggests that perceived intensity is a power function of the physical intensity of the stimulus. Gustav Fechner was a philosopher who was pondering the mind- body problem in philosophy and believed he had discovered a proof of the existence of God by discovering a mathematical relationship between mind (perception) and body (physical stimulus).