Gustav Theodor Fechner

German experimental psychologist who founded psychophysics and formulated Fechner's law, a landmark in the emergence of psychology as an experimental science.

Gustav Theodor Fechner was born on April 19, 1801, in a small town in southeastern Germany, Lower Lusatia. He earned his degree in biological science in 1822 at the University of Leipzig and taught there until his death on November 18, 1887. Having developed an interest in mathematics and physics, he was appointed professor of physics in 1834.

Around 1839 Fechner had a breakdown. He had injured his eyes by gazing directly at the sun while experimenting with afterimages, and his response was to isolate himself from the world for three years. During this period his interest in philosophy increased. Fechner believed that everything is endowed with a soul; nothing is without a material basis; and, although seen from different perspectives, mind and matter are the same essence. In addition, he believed that the foregoing assertions were demonstrable and provable by means of psychophysical experiments in psychology. He authored many books and monographs on such diverse subjects as medicine, aesthetics, and experimental psychology, affixing the pseudonym Dr. Mises to some of them.

The penultimate philosophic problem that intrigued Fechner, and for which his psychophysics was intended to be a solution, was the age-old mind-body dilemma. His solution has been called the identity hypothesis: mind and body are not regarded as a true duality, but are different sides of one reality. They are separated in the form of sensation and stimulus; that is, what appears from a subjective viewpoint as the mind, appears from an external or objective viewpoint as the body. In the expression of the equation of Fechner's law (sensation intensity = C log stimulus intensity), it appears evident that the dualism is not real. While this law has been criticized as having flawed logic, and for not having universal applicability, it has been useful in research on hearing and vision.

Gustav Theodor Fechner.

Gustav Theodor Fechner.
(Photograph by Georg Brokesh. The Library of Congress.)

Fechner's most significant contribution was made in his Elemente der Psychophysik (1860), a text of the “exact science of the functional relations, or relations of dependency, between body and mind,” and in his Revision der Hauptpunkte der Psychophysik (1882). These texts were considered his masterworks and led to his renown as a psychologist; in them he created, developed, and established new methods of mental measurement, and laid the foundation for quantitative experimental psychology. The three methods of measurement were the method of just-noticeable differences, the method of constant stimuli, and the method of average error. According to academicians, the method of constant stimuli, also known as the method of right and wrong cases, has become the most important of the three methods. It was further developed by G. E. Muller (1850–1934) and F. M. Urban (1878–1964).

See also Experimental psychology ; James, William; Psychophysics ; Statistics in psychology .



Brace, Nicola, and Jovan Byford. Investigating Psychology: Key Concepts, Key Studies, Key Approaches. Oxford, UK: Oxford University Press, 2012.

Fechner, Gustav Theodor, Alfred Jarry, and Robert Irwin. The Comparative Anatomy of Angels. London, UK: Institutum Pataphysicum Londininese, 2010.

Fechner, Gustav Theodor. On Life After Death. General Books, 2010.

Hall, G. Stanley. Founders of Modern Psychology. Whitefish, MT: Kessinger Pub, 2009.

Kardas, Edward P. History of Psychology: The Making of a Science. Wadsworth, 2013.

Solomon, Joshua A. Fechner's Legacy in Psychology: 150 Years of Elementary Psychophysics. Leiden, Germany: Brill, 2011.


Hawkins, Stephanie L. “William James, Gustav Fechner, and Early Psychophysics.” Frontiers in Physiology 2 (2011): 68-97, doi: 10.3389/fphys2011.00068

WEBSITES “Gustav Theodor Fechner.” (accessed November 12, 2014).

psychclassics. “Classics in the History of Psychology: Elements of Psychophysics (Sections VII and XVI), Gustav Theodor Fechner (1860/1912).” (accessed November 12, 2014).