The adjectival "symbolic" is often used by Lacan in a fairly conventional sense, but in the 1950s he begins to use the word as a substantive, and it rapidly becomes the cornerstone of his theory: the subject's relationship with the symbolic is the heart of psychoanalysis.
He also demonstrates that in primitive societies the ritual exchange of gifts has an important role in the creation and perpetuation of social stability.
Adapting Lévi-Strauss's study of how kinship rules and exogamy govern exchanges between human groups to the field of psychoanalysis, Lacan now describes the Oedipus complex as a process which imposes symbolic structures on sexuality and allows the subject to emerge.
Pre-oedipal sexuality is likened to a state of nature and unbridled sexuality; the role of the Name-of-the-Father is to disrupt the dual relationship in which the child tries to fuse with the mother in an incestuous union, and to establish a legitimate line of descent ("son of...", "daughter of...").
Although the exchange of signifiers in speech is an obvious example of symbolic exchange, Lacan's symbolic is not simply synonymous with language, and should be understood as comprising the entire domain of culture.