He also challenged faith in reason. Freud thought that the subconscious mind drives much of human behavior. He said that learned social values like morality and reason help people to control powerful urges. An individual, however, feels constant tension between repressed drives and social training. Freud argued that this tension may cause psychological or physical illness. Freud pioneered psychoanalysis. This is a method of studying how the mind works and treating mental disorders. Although many of his theories have been discredited, it is said that Freud's hypothesizes have had a huge impact far beyond medicine.