Abstract: The purpose of this article is to evaluate a psychologist and analyze the impact of his theories on society at large. Sigmund Freud, one of the most recognized names in the field of psychology to date, had developed some eccentric theories that many scientists still accept as having a factual basis. His theories on hypnotherapy, psychosexual development, and defense mechanisms give people the ability to control and predict their future behavior. These theories, recognized as among the most notable and influential, transformed a generation of free thinkers and scientists. His ideas paved the way for what is now universally known as the field of psychology. Sigmund Freud, known as one of the most influential psychologists the world has ever seen, was born in 1856 in the town of Freiberg in the Austro-Hungarian Moravian Empire. Freiberg was a city of trees and nature and Freud always felt connected to his surroundings. His father gave birth to two sons in his first marriage, twenty years before Sigmund's birth. His first wife later died and he remarried. Sigmund was born to his father's second wife, Amelia, and later gave birth to seven more children (Chiriac). When Sigmund was four years old his family moved to Vienna due to a business failure. They settled in a small apartment in the busy and noisy city. Freud then recalls how Vienna is different from the place where he was born: “I have never felt completely at ease in this city. I think today I have always missed the wonderful forests of my childhood, and one of my memories evokes the fact that I ran as if I wanted to get down to my father, when I could barely walk..." (Chiriac). Even if his family did not have many ...... half of documents ...... based solely on medical observation or genetic inheritance. Through theories such as stages of psychosexual development, Freudian errors, the id, l 'ego, superego and even defense mechanisms, we are able to see ourselves as beings capable of predicting behavior and controlling it. This, of all things, is the most important and essential to human life. Works citedChiriac , Jean. The childhood of Sigmund Freud." Freud Files. AROPA, Web. 20 Nov 2009.."Defense mechanisms." SAU Department of Behavioral and Social Sciences. Web. 22 Nov2009.ml>.Freud, Sigmund. The interpretation of dreams. New York: Macmillan, 1900. Print. "Sigmund Freud". NNDB Tracking the World, Web 15 November 2009..