Mental energy or psychic energy is a concept in some psychological theories or models of a postulated unconscious mental functioning on a level between biology and consciousness.
The idea harks back to Aristotle's conception of actus et potentia. "Energy" here used in the literal meaning of "activity" or "operation". Henry More, in his 1642 Psychodia platonica; or a platonicall song of the soul, defined an "energy of the soul" as including "every phantasm of the soul". Julian Sorell Huxley defines "mental energy" as "the driving forces of the psyche, emotional as well as intellectual" (On living in a revolution xv.192, 1944).
In 1874, the concept of "psychodynamics" was proposed with the publication of Lectures on Physiology by German physiologist Ernst Wilhelm von Brücke who, in coordination with physicist Hermann von Helmholtz, one of the formulators of the first law of thermodynamics (conservation of energy), supposed that all living organisms are energy-systems also governed by this principle. During this year, at the University of Vienna, Brücke served as supervisor for first-year medical student Sigmund Freud who adopted this new "dynamic" physiology. In his Lectures on Physiology, Brücke set forth the then-radical view that the living organism is a dynamic system to which the laws of chemistry and physics apply.
In The Ego and the Id, Freud argued that the id was the source of the personality's desires, and therefore of the psychic energy that powered the mind. Freud defined libido as the instinct energy or force. Freud later added the death drive (also contained in the id) as a second source of mental energy. The origins of Freud's basic model, based on the fundamentals of chemistry and physics, according to John Bowlby, stems from Brücke, Meynert, Breuer, Helmholtz, and Herbart.
In 1928, Carl Jung published a seminal essay entitled "On Psychic Energy". Later, the theory of psychodynamics and the concept of "psychic energy" was developed further by those such as Alfred Adler and Melanie Klein.
Just as physical energy acts upon physical objects, psychological energy would act upon psychological entities, i.e. thoughts. Psychological energy and force are the basis of an attempt to formulate a scientific theory according to which psychological phenomena would be subject to precise laws akin to how physical objects are subject to Newton's laws. This concept of psychological energy is completely separate and distinct from (or even opposed to) the mystical eastern concept of spiritual energy.
The Myers–Briggs Type Indicator divides people into 16 categories based on whether certain activities leave them feeling energized or drained of energy.
Mental energy has been repeatedly compared to or connected with the physical quantity energy.
Studies of the 1990s to 2000s (and earlier) have found that mental effort can be measured in terms of increased metabolism in the brain. The modern neuroscientific view is that brain metabolism, measured by functional magnetic resonance imaging or positron emission tomography, is a physical correlate of mental activity.
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