Sigmund Freud was a leading theorist of psychological research in his time and remains a foundational figure in the field. Drawing from the research of others in his field and his own clinical practice as a psychoanalyst, Freud developed a theory of meta-psychology, or a framework of the structures that make up the human psyche. The Ego and the Id (1923) is Freud’s last meta-psychological text and foundational to Freudian theory. The concise essay describes Freud’s model of the psyche and how the different components interact as part of a dynamic system. In the work, Freud builds on aspects of the psyche common to the field of psychology at the time and his own theories as laid out in earlier works like The Interpretation of Dreams (1899), Psychology of the Unconscious (1912), and Beyond the Pleasure Principle (1920).

Freud’s early work in psychoanalysis was focused on two broad principles: the notion that the psyche is divided between the conscious and unconscious and the notion that the psyche is driven by the pleasure principle. The pleasure principle is the theory that the psyche seeks out things that are pleasurable and avoids things that cause displeasure. In Beyond the Pleasure Principle, Freud explores in detail the role of the pleasure principle and the related life drive, Eros, in the psyche. In the final chapter of this work, Freud concludes that the pleasure principle alone is not sufficient to understanding the psyche. He theorizes that there is a conflicting and complementary death drive at work: that is, a desire to return to the inanimate and universal state from which individual life arises.

In The Ego and the Id, Freud clarifies the tripartite structure of the psyche—the id, the ego, and the superego—developed in his previous work. The id is the unconscious source of impulses; the ego is the conscious mind that governs self; and the superego is the ego ideal, the ideal state to which the ego aspires. The ego mediates between the demands of the id and the superego. Freud describes the dynamics of this system as it responds to the two dominating drives, the life drive and the death drive. He also clarifies the broad distinction between the conscious and unconscious by adding the category of preconscious, or latent thoughts, that can be easily recalled to the conscious mind.

Today, over 100 years since the publication of The Ego and the Id, psychologists do not rely wholesale on Freud’s theories and insights in research or practice. Freud’s ideas about the psychical biology of the body and its relationship to the psyche were seen as dated even in his own time, such as his outmoded theories about neuron function. Psychologists today rely much more on biological insights to understand mental illness. Although no longer seen as entirely scientifically valid, elements of his meta-psychology are still fundamental to the field, such as the understanding that humans have impulses of which they are unaware and that talk therapy can help patients better understand and manage those impulses. Further, Freud’s theories and ideas have had a pervasive effect on Western culture, the arts, and the medical field. His theories, including the construction of the psyche, Oedipal conflict, repression, and dream interpretation, are used to understand literature, history, and film. The surrealist movement in art and film, championed by artists such as Salvador Dalí, André Breton, Leonor Fini, and Meret Oppenheim, aimed to externalize the activity of the unconscious. Alfred Hitchcock’s Psycho and Park Chan-Wook’s Old Boy are among many classic film that draw upon Freud’s theory of the Oedipus complex.