A further influence came in the form of physics. The second half of the nineteenth century, during which Freud did most of his important work, saw great advances in physics. According to Thornton, the discovery mostly responsible for this was Helmholz's principle of conservation energy. Helmholz held that the total amount of energy in a physical system is constant; that it could be changed but not annihilated; and that when the energy is moved from a part of the system, it would reappear in another part. This principle influenced areas such as thermodynamics, electromagneticism, and nuclear physics. The 19th century therefore saw major discoveries that changed the world. For Freud, this meant that his field of study was significantly influenced by the principle. At the University of Vienna, for example, Freud's professor, Ernst Brucke published a book promoting the energy conservation principle as applied to human beings. According to the professor, all living beings, including human beings, were essentially energy systems. Freud enthusiastically adopted this new principle, which he termed "dynamic physiology."

Freud used this principle to develop his idea of "psychic energy," which holds that the human personality itself is also an energy system. This became the main principle of Freud's psychoanalytic theory. For Freud, psychic energy functioned upon the principle that the modifications, transmissions and conversions of psychic energy shaped and determined personality...

However, he remains a major figure and pioneer in the field. His enthusiasm for the science of his time, as well as his drive to use himself as the subject of his first analytical experiment, is a true example to the scientists and psychological experts of today. Even up to the end of his life, he showed an adherence to his principles, beliefs, and his own energy systems that is admirable even today.
Even if many advances have been made in the field of psychoanalysis, Freud will always remain at the birth of the field, offering an exemplary attitude of enthusiasm and commitment, even if some of his ideas were later proved incorrect or at least fallible.

References

Boeree, C.G. (2009). Personality Theories: Sigmund Freud. Retrieved from http://webspace.ship.edu/cgboer/freud.html

Chiriac, J. Freud and the "Cocaine Episode" Retrieved from http://www.freudfile.org/cocaine.html

Gay, P. (2999, Mar 29). Scientists and Thinkers: Sigmund Freud. The Time 100. Retrieved from http://205.188.238.181/time/time100/scientist/profile/freud.html

NNDB. (2010). Sigmund Freud. Retrieved from http://www.nndb.com/people/736/000029649/

Thornton, S.P. (2005). Sigmund Freud (1856-1939). Internet Encyclopedia of Philosophy. Retrieved from http://www.iep.utm.edu/freud/