If James and Wundt are the fathers of psychology, Freud can best be described as psychology’s slightly senile great-uncle.
A surprising thing about Freud is that he originally intended to be a medical psychopathologist, and was only directed towards his famous approach by his mentor Joseph Breuer. Breuer and Freud collaborated studying “Anna O.”, who developed many different hysterical symptoms after caring for her ill father for months. They found she would go into states that looked like trances and during them would recall memories related to her current symptoms. The symptoms would then disappear afterwards, to be replaced by new ones. Anna called this “chimney sweeping”, and this treatment was probably what inspired Freud to keep studying the hysterical, irrational aspects of the mind.
After Anna was believed to be cured (despite falling in love with her therapist to the point where she was convinced she was pregnant with his child), Freud began to develop his theories of the unconscious and sexuality.
His main techniques were free association and dream analysis. To him everything was connected, and everything happened for a reason, so even the smallest of verbal slips could be seen as a mask hiding a secret wish or resentment.
That leads to one of the problems with Freud’s therapy: everything “discovered” in a therapy session is inferred and interpreted, and there is no way of proving the events in a patient’s mind happened in the way they believe it did.
One legacy of Freud’s research is its shock value- for a figure in Victorian society to claim that even small children had sexual instincts, and that those instincts were a foundation of people’s behaviour, was unthinkable to the majority of people. At the time, people were believed to be rational and self-aware, so the idea of only a tiny part of the mind being conscious, and the rest filled with unknown and uncontrollable drives, was also controversial.
Freud’s influence is mostly seen in today’s pop culture, rather than today’s psychology; the therapy couch, image of the therapist, and use of his terms in conversation (e.g. Freudian slip) are prevalent in pop-psychology, to the point where Freud can often appear to be more of a caricature than a person.
However, he left a lasting impression on psychology in the form of talking therapies. He tends to be psychological marmite, inspiring either adulation or hatred from students.
Despite many people hating his theories or methods, both supporters and detractors usually agree that Freud was instrumental to the development of psychology as he (in a similar but bigger way to William James) changed the public opinion of psychology from a dry laboratory science followed by only a few people, to a popular and personal exploration of the mind. For this reason, Freud is still one of the worlds greatest psychologists and essential enough to the story that he is still is taught in the majority of psychology courses.