Gustav Theodor Fechner (/ˈfɛxnər/; German: [ˈfɛçnɐ]; 19 April 1801 – 18 November 1887),[1] was a German philosopher, physicist and experimental psychologist. An early pioneer in experimental psychology and founder of psychophysics, he inspired many 20th century scientists and philosophers. He is also credited with demonstrating the non-linear relationship between psychological sensation and the physical intensity of a stimulus via the formula: {\displaystyle S=K\ln I} {\displaystyle S=K\ln I}, which became known as the Weber–Fechner law.