Jacques Lacan differentiated between an imaginary identification, that forms the ego from a symbolic one that founds the subject. He discussed the first in his essay on the "Mirror Stage" (1936) and he examined the second primarily in his seminar on Identification (1961-1962).

Imaginary identification involves the image of one's "fellow being." Before the subject develops the proper neurological connection, he grasps the unity of his body image by identifying with the image of the other, the ideal ego. Thus the subject escapes the feeling of having a fragmented body. The mirror stage is also the source of the aggressive tension that characterizes relations with the one's fellow being, and it is the source of desire as the other's.

Symbolic identification, or "signifier identification," involves an ideal signifier—an insignia of the Other or a unary trait—as the nucleus of the ego-ideal that the subject depends...