the Austrian physician Sigmund Freud developed psychoanalysis,

a method of investigation of the mind and the way one thinks

a systematized set of theories about human behavior

and a form of psychotherapy to treat psychological or emotional distress

especially unconscious conflict.

Freud's psychoanalytic theory was

largely based on interpretive methods

introspection and clinical observations.

It became very well known

largely because it tackled subjects such as

sexuality, repression, and the unconscious mind as

general aspects of psychological development.

These were largely considered taboo subjects at the time

and Freud provided a catalyst for them to

be openly discussed in polite society.

Clinically, Freud helped to pioneer the method of free association

and a therapeutic interest in dream interpretation.

Freud had a significant influence on Swiss psychiatrist Carl Jung

whose analytical psychology became an

alternative form of depth psychology.

Psychoanalytic theory and therapy were criticized by psychologists such as Hans Eysenck

and by philosophers including Karl Popper.

Popper, a philosopher of science, argued that psychoanalysis

had been misrepresented as a scientific discipline

whereas Eysenck said that psychoanalytic tenets

had been contradicted by experimental data.

By the end of 20th century, psychology departments in

American universities had become scientifically oriented

marginalizing Freudian theory and dismissing it as a

"desiccated and dead" historical artifact.

Meanwhile, however, researchers in the emerging

field of neuro-psychoanalysis defended some of

Freud's ideas on scientific grounds

while scholars of the humanities maintained that Freud

was not a "scientist at all, but ... an interpreter."