Biography

Sigmund Freud was born in Austria in 1856. He grew up in a traditional family and studied medicine in Vienna. In the beginning of his career, Freud did a lot of research on the field of neurology.
During a study-related trip to Paris in 1885 he met the neurologist Jean-Marie Charcot. Because of conversations Freud had with Charcot, he developed a different view on mental disorders. Charcot was familiar with clinical methods like hypnosis and he was interested in hysteria. Together with Josef Breuer Freud completed his new theories. These theories became very famous, because they where very different from the contemporary alternative theories. Freud became well-known for his emphasis on the human unconsciousness. This was unacceptable for many researchers, because of the difficulty involved in measuring the concepts Freud used. Although the theories of Freud became increasingly more famous, Breuer also disagreed with Freud more. They eventually went their own way.
Freud became a teacher in Vienna and worked together with Carl Gustav Jung (who would later also disagree with Freud). In the 20th century Freud wrote a lot of books and completed many theories. He was criticized a lot, not only because little empirical evidence for his theories was found, but also because of his emphasis on sexuality. Especially in the 20th century, this was very controversial. In spite of his critics, he was also admired. His theories had a big impact on the scientific literature, because of the new concepts Freud introduced. In 1938, Freud moved to London where he lived until his death in 1939.

Theory

The most important contribution of Freud is his division of the human psyche in three different energies: Id, Ego and Superego.
Id is an unconscious mechanism that works on two energy sources. The first is Eros, the sexual life energy. The second is Tanatos, the anger, or death energy.
Ego tries to keep these two energy sources in balance. This is why people in general function well in society. On the other hand, when Ego does not work correctly, human behavior is controlled by Id. This happens when people are asleep. This is why dreams are an important information source. In dreams, the unconscious needs of a person become visible. Fortunately, Ego is sufficiently strong to suppress these unconscious urges.
The Superego is the mental image that people have of their ideal self. Superego contains the norms and values that are passed to a person by people in his/her environment. Thus, Superego is the opponent of Id. Ego guides behavior in such a direction, that both the desires of Superego and Id are satisfied.

Freud also introduced an influential theory of human development. According to this theory mental disorders are caused by events in the early child years (before the age of six). A mental disorder can evolve when a child does not complete one of the five stages of childhood. These stages are named respectively the oral stage, the anal stage, the phallic stage, the latent stage, and the genital stage.
One sub theory about the phallic stage is very well-known. During the phallic stage, a child develops a sex-identity. In this stage, a boy develops the oedipus complex. On an unconscious level, he falls in love with his mother. He realizes that his mother loves his father and hates his father for it. The oedipus complex is solved when the boy understands that he has to become just like his father to impress his mother. Thus, his hatred towards his father is transformed in an identification with his father. The female version of the oedipus is called the elektra complex.

When Freud introduced his theories they where taken literary by a lot of people. After a wave of criticism, mainly about the lack of empirical support for his theories, Freud emphasized that his theories where symbolic in nature.
Although some therapists still use Freudian theories, Freud value to the field of psychology lies in the new concepts he introduced.

Research and experiments

As mentioned before, in the beginning of his career Freud did a lot of medical research on the field of neurology. The theories that made him famous were written many years later. The research methods where primarily clinical. In conversations with patients, the thoughts of a patient were analyzed to gain insight in the behavior pattern of that patient. Today, the lack of empirical support is still the greatest criticism on Freud.