The mirror stage is a concept in the psychoanalytic theory of Jacques Lacan. Philosopher Raymond Tallis describes the mirror stage as "the cornerstone of Lacan’s oeuvre. " Initially, Lacan proposed that the mirror stage was part of an infant's development from 6 to 18 months, as outlined in his first and only official contribution to larger psychoanalytic theory at the Fourteenth International Psychoanalytical Congress at Marienbad in 1936...