Gustav Theodor Fechner (/ˈfɛxnər/; German: [ˈfɛçnɐ]; 19 April 1801 – 18 November 1887) was a German experimental psychologist,philosopher, and physicist. 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: , which became known as the Weber–Fechner law.