Gustav Fechner



Gustav Theodor Fechner (April 19, 1801 – November 28, 1887), was a German experimental psychologist. A pioneer in experimental psychology and founder of psychophysics, he inspired many 20th century scientists and philosophers, including the philosopher Professor Gerardus Heymans, Ernst Mach, Wilhelm Wundt, Sigmund Freud, and G. Stanley Hall. He is also credited to have created the formula "$$S = K Log I$$" that proved the existence of a scientific connection between the body and the mind.

He was born at Gross-Särchen, near Muskau, in Lower Lusatia, where his father was pastor. He was educated at Sorau and Dresden and at the University of Leipzig, the city in which he spent the rest of his life. In 1834 he was appointed professor of physics, but in 1839 contracted an eye disorder while studying the phenomena of colour and vision, and, after much suffering, resigned. Subsequently recovering, he turned to the study of the mind and its relations with the body, giving public lectures on the subjects dealt with in his books.

Contributions
Gustav Fechner authored the following works:
 * Das Büchlein vom Leben nach dem Tod (1836, 5th ed., 1903), which has been translated into English
 * Nanna, oder über das Seelenleben der Pflanzen (1848, 3rd ed., 1903)
 * Zendavesta, oder über die Dinge des Himmels und des lenseits (1851, 2nd ed. by Lasswitz, 1901)
 * Uber die physikalische und philosophische Atomenlehre (1853, 2nd ed., 1864)
 * Elemente der Psychophysik (1860, 2nd ed., 1889)
 * Vorschule der Ästhetik (1876, 2nd ed., 1898)
 * Die Tagesansicht gegenüber der Nachtansicht (1879).

He also published chemical and physical papers, and translated chemical works by J. B. Biot and Louis Jacques Thénard from the French language. A different but essential side of his character is seen in his poems and humorous pieces, such as the Vergleichende Anatomie der Engel (1825), written under the pseudonym of "Dr. Mises."

Fechner's epoch-making work was his Elemente der Psychophysik (1860). He starts from the Spinozistic thought that bodily facts and conscious facts, though not reducible one to the other, are different sides of one reality. His originality lies in trying to discover an exact mathematical relation between them. The most famous outcome of his inquiries is the law known as the Weber–Fechner law which may be expressed as follows:


 * "In order that the intensity of a sensation may increase in arithmetical progression, the stimulus must increase in geometrical progression."

Though holding good within certain limits only, the law has been found to be immensely useful. Fechner's law implies that sensation is a logarithmic function of physical intensity, which is impossible due to the logarithm's singularity at zero; therefore, S. S. Stevens proposed the more mathemtically plausible power-law relation of sensation to intensity in his famous paper entitled "To Honor Fechner and Repeal His Law."

Fechner's general formula for getting at the number of units in any sensation is S = c log R, where S stands for the sensation, R for the stimulus numerically estimated, and c for a constant that must be separately determined by experiment in each particular order of sensibility. Fechner's reasoning has been criticized on the grounds that although stimuli are composite, sensations are not. "Every sensation," says Professor James, "presents itself as an indivisible unit; and it is quite impossible to read any clear meaning into the notion that they are masses of units combined."

He also studied the still-mysterious perceptual illusion of Fechner color, whereby colours are seen in a moving pattern of black and white.

Influence
Fechner, along with Wilhelm Wundt and Hermann Helmholtz is recognized as one of the founders of modern, experimental psychology. His clearest contribution was the demonstration that because the mind was susceptible to measurement and mathematical treatment, psychology had the potential to become a quantified science. Theorists such as Immanuel Kant had long stated that this was impossible, and that therefore, a science of psychology was also impossible. Fechner also paved the way for Sigmund Freud's study of the unconscious with his eight volume collection entitled: "Philosophy of the Unconscious", and "The Book of It" which Freud later used to create his theory of the id.

Though he had a vast influence on psychophysics, the disciples of his general philosophy were few. His world concept was highly animistic. He felt the thrill of life everywhere, in plants, earth, stars, the total universe. Man stands midway between the souls of plants and the souls of stars, who are angels. God, the soul of the universe, must be conceived as having an existence analogous to men. Natural laws are just the modes of the unpholding of God's perfection. In his last work Fechner, aged but full of hope, contrasts this joyous "daylight view" of the world with the dead, dreary "night view" of materialism. Fechner's work in aesthetics is also important. He conducted experiments to show that certain abstract forms and proportions are naturally pleasing to our senses, and gave some new illustrations of the working of aesthetic association.

Fechner's position in reference to predecessors and contemporaries is not very sharply defined. He was remotely a disciple of Schelling, learnt much from Johann Friedrich Herbart, Schopenhauer, and Christian Hermann Weisse, and decidedly rejected Georg Hegel and the monadism of Rudolf Hermann Lotze.

Modern discussions
Fechner's introduction of quantitative methods into psychology is discussed by
 * Heidelberger, M. (2001) Gustav Theodor Fechner, Statisticians of the Centuries (ed. C. C. Heyde and E. Seneta) pp. 142-147. New York: Springer.


 * Stephen M Stigler. The History of Statistics: The Measurement of Uncertainty before 1900, Cambridge, MA: Harvard University Press 1986. pp. 242-254.

The standard intellectual biography of Fechner and his work in English is
 * Michael Heidelberger. Nature From Within: Gustav Theodor Fechner and his Psychophysical Worldview Trans. Cynthia Klohr. Pittsburgh, PA: University of Pittsburgh Press, 2004.