Sigmund Freud (1986 – 1939) is hailed as the Father of Psychology. He out forth many new concepts about sexuality, consciousness and instincts. He spent his whole life devoted to discovering the secrets of human nature.
Image source; blogs.scientificamerican.com/literally-psyched/files/2012/07/William_James_in_1890s.jpg
In 1900, he published his seminal work, Dir Traumdeutung (The Interpretation of Dreams), arguing that dreams, like neuroses, are disguised manifestations of repressed sexual desires.