In psychodynamics, psychic energy or psychological energy refers to the effect of the principle of conservation of energy, the first law of thermodynamics, or of energy theories in general in a psychological system. In his 1976 article "Psychic Energy: A Historical Perspective", American psychiatrist Robert Galatzer-Levy argues that: [3]

“Much criticism of the concept of psychic energy is based on its apparent failure to live up to the paradigm on which it is modeled, the concept of energy conservation in physics.”

History
The psychic energy model first entered psychology and physiology through the interactions of German physicians Ernst Brücke, Herman Helmholtz, and Emil Du Bois-Reymond, who during the years 1838-42, worked in the laboratory of the German physiologist Johannes Muller. In opposition to Muller’s adherence to the principle of vitalism, a doctrine that the functions of a living organism are due to a vital principle distinct from physiochemical forces, the three of them, in the words of Du Bois-Reymond, formulated a desire to validate the basic truth that: [1]


This force or kraft, as it is called in German, soon later became synonymous with the newly forming concept of energy. This concept was soon carried over into psychology by Austrian psychologist Sigmund Freud, Brücke’s medical school student, and later by Freud’s protégé Swiss psychologist Carl Jung. One of the first to explicitly define the concept of psychic energy, according to Jung, was Russian psychologist Nicolas von Grot, who in 1898 stated: [2]

“The concept of psychic energy is as much justified in science as that of physical energy, and psychic energy has just as many quantitative measurements and different forms as has physical energy.”

References
1. Helmholtz, Hermann von (biography). Encyclopedia Britannica Deluxe Edition (2002), CD-ROM.
2. (a) Von Grot, Nicolas. (1898). “Die Begriffe der Seele und der psychischen Energie in der Psychologie”, Archiv fur systematische Philosophie, IV.
(b) Jung, Carl. (1928). “On Psychic Energy”, in On the Nature of the Psyche (1960). Princeton University Press.
(c) Bishop, Paul. (1999). Jung in Contexts (pg. xxiii). Routledge.
3. Galatzer-Levy, Robert M. (1976). “Psychic Energy: A Historical Perspective”, The Annual of Psychoanalysis, 4: 41-61.

Further reading
● Schwartz, Nathan J. (1969). Entropy, Negentropy, and the Psyche: an Inquiry into the Structure of Psychic Energy. Publisher: s.n.
● Hall, Calvin S. and Nordby, Vernon J. (1973). A Primer in Jungian Psychology (section II: Psychic Energy, pgs. 59-60). New York: Meridian Books.
● Csíkszentmihályi, Mihály. (1990). Flow – the Psychology of Optimal Experience (section: Attention as Psychic Energy, pgs. 30-33). Harper Perennial.