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Freud's Psycho Dynamic Theory
Freud theorized that the human personality has three distinctive and interacting parts and he used thermodynamics as an extended metaphor to explain this. Using this tripartite division, in 1923 Freud published the ground-breaking book: "The ego and the id" in which he named these three distinctive parts, the id, the ego, and the superego:
Sigmund Freud lived from 1856-1939. He was born in the Czech Republic. When he was young, he moved with his family to Germany, then again to Vienna, where he settled and spent most of his life. During much of Freud's life, the dominant technology was steam power. Steam was commonly the source of energy to power machinery. People traveled by steam engines and steam boats and they worked in factories on machinery powered by steam. Steam power was as common back then as computers are for us today.
Sigmund Freud [1856-1939]
During these years, Freud was greatly influenced the works of a scientist named Hermann von Helmholtz, whose interests were in physics, physiology and psychology. The laws of thermodynamics were of great interest to von Helmholtz and thus Freud also showed a great interest in the thermodynamics of steam power. He saw similarities between thermodynamics and the human personality. Freud used an analogy of thermodynamics to explain his newly developing theories of psycho-dynamics.
Hermann von Helmholtz [1821-1894]
 The id, Freud described as our biological needs and drives, as: hunger, thirst, and sex, etc. The id provides energy for the system just as fire provides energy in thermodynamics.
 The superego, Freud explained as society's rules, our voice of conscience. In thermodynamic terms, the superego would be a lid on the apparatus that contained water, which was to be converted into steam.
 The ego is the conscious mind that contains one's thoughts, judgments and memories. In Freud's thermodynamic metaphor, the ego was the wheels and the escape valves where the steam is released.
Freud broke down his personality idea from parts that cannot be directly observed into a tangible model of energy heating water and being released as steam. Freud examined the first law of thermodynamics and applied this to his psycho-dynamics theories. The first law of thermodynamics states that:
"Energy can neither be created nor destroyed"
Freud theorized this to be true with the human personality and adopted Darwin's assumption that emotion is a form of physical energy . Hence, 'psychic energy' can neither be created nor destroyed, it can only be converted from one form to another. He believed that much of one's personalities are shaped from one's childhood experiences. He theorized that from a child's birth until the child has gone through puberty, he or she goes through psychosexual stages of development. The id's "pleasure seeking energy" centers on different pleasure-sensitive zones of the body during different stages in a child's life.
 (a) Contract Author [essay] (2003). [URL] "Relationship Between Freud's Psycho Dynamic Theories and Thermodynamics" [www.learnessays.com].
 Freud, S. (1923). The Ego and the Id. New York: W.W. Norton & Company.
 Hall, C.S. & Nordby, V.J. (1999). A Primer of Jungian Psychology. New York: Meridian.
The first stage, which lasts until the child is about eighteen months old is the oral stage, which centers on the mouth. From eighteen months to three years old, is the anal stage with stimulation of the bladder and bowels bringing gratification. From about three to six years old the pleasure-seeking zone moves to the genitals. This is called the phallic stage. The next stage is called the latency period. During this time, a child's sexuality is torpid. When a child reaches puberty, he or she enters the genital stage and begins to feel sexual feelings toward others.
Freud believed that an adult's personality developed because of how a child dealt with conflicts during any one particular psychosexual stage. He suggested that negative energy or anxiety from our childhood conflicts could not be destroyed, just as the first law of thermodynamics states . This anxiety is pushed down out of consciousness. He called this defense mechanism, repression. Freud used projective techniques such as showing his patients ambiguous pictures and would try to get the patient to tell a story about them. If a theme appeared from the patient's responses, he would explore these themes as a way to find out what had been buried in the unconscious.
To create a psycho-dynamic paradigm that was tangible to the scientific community of his day, Freud constructed an analogy between thermodynamics and his psycho-dynamic model. Freud believed only one's ego is in direct contact with the world. He felt that much of the human personality was hidden below the surface in our unconsciousness. He believed that the ego dealt with reality anxiety, whereas the id dealt with neurotic anxiety and the superego with moral anxiety. The anxieties of the id and the superego are, Freud believed, the result of conflict during a childhood psychosexual stage of development. Unfortunately, these anxieties cannot be destroyed. Energy, according to the analogy, can neither be created nor destroyed.
The anxieties of the id and the superego are often repressed into the unconsciousness as a protective defense mechanism. The ego, the part of personality we can see, can show symptoms of anxiety either acknowledged or repressed, just as an escape valve can release steam.
Freud's psycho dynamic model may seem opaque to us today because he explained it in terms of the technology metaphor of his day. It is as if a scientist today used a current technology such as computers as a metaphor for things that we cannot explain easily. However, Sigmund Freud, although criticized, is a highly respected pioneer of psychology. The dominant paradigm of clinical work of psychiatry and psychology is Freudian work. In sum, Freud's theory of the unconscious assumes a private, personal mind; a mind populated with wishes, desires, and needs that have a biological, intra-psychological origin, and which follow endemic mechanical laws .
Ernst von Brucke [1819-1892]
The principle of conservation states, in effect, that the total amount of energy in any given physical system is always constant, that energy quanta can be changed by not annihilated, and consequently that when energy is moved from one part of the system it must reappear in another part. The acquisition of this principle into a fundamental law was a dominant driving force during the mid 19th century forwarded by those as Hess (1840), Mayer (1841), Joule (1843), Helmholtz (1847), and Clausius (1850).
In 1873, at the University of Vienna’s medical school, Freud did research in physiology for six years under the German scientist Ernst Brucke. Brucke had previously worked with Helmholtz, along with Emil Du Bois-Reymond, the founder of experimental neurophysiology, during the years 1838-42, 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 “in an organism no other forces have effect than the common physiochemical ones.”
In 1874, Brucke published a book setting the view that all living organisms, including the human one, are essentially energy-systems to which, no less than to inanimate objects, the principle of the conservation of energy applies. Freud, who had great admiration and respect for Brucke, quickly adopted this new ‘dynamic physiology’, with enthusiasm; in doing so, he resultantly developed the science of "psycho-dynamics"; the etymology of which stems from or is a spinoff of the 1860 publication of Elemente der Psychophysik (Elements of Psychophysics) by German physicist and psychologist Gustav Fechner.
Within certain limits, this law has been found immensely useful. From the tenable theory that the intensity of a sensation increases by definite additions of stimulus, Fechner was led on to postulate a "unit of sensation", so that any sensations might be regarded as composed of n units. With sensations, he argued, thus being representable by numbers, psychology may become an "exact" science, susceptible of mathematical treatment. The summation of this principle with the principle of energy conservation, dictates, according to Freud, that society cannot eliminate the impulses it condemns; society can only make individuals unconscious of the impulses which nevertheless continue to assert their influence in disguised forms .
From here, Freud grounded the principle that there is such a thing as ‘psychic energy’, that the human personality is also an energy-system, and that it is the function of psychology to investigate the modifications, transmissions, and conversions of psychological energy with the personality which shape and determine it .
Gustav Fechner [1801-1887]
Freud, in his beginnings, was significantly influenced by the logic of Fechner, who, based on the theories of Spinoza, theorized that bodily facts and conscious facts, though not reducible one to the other, are different sides of one reality; which, according to Gustav, should be mathematically related. The famous outcome of his inquiries is the law known as Weber's or Fechner's law:
"In order that the intensity of a sensation may increase in arithmetical progression, the stimulus must increase in geometrical progression."
The following 2005 article (shown below), outlining Austrian psychologist Sigmund Freud's 1920 "dynamic psychology" model, was referenced and explained, in detail, in the section "Psychodynamics" (pgs. 675-77), of the 2007 textbook Human Chemistry (Volume Two) by American chemical engineer Libb Thims, shown below right: