The mirror stage is one of Jacques Lacan’s most significant contributions to psychoanalytic theory. It accounts for the formation of the ego (the rational, self-conscious part of the mind) and occurs between the ages of six and eighteen months.

Infants enter the mirror stage when they begin to understand that the image seen in a mirror is an image of their own bodies. This recognition is associated with pleasure. During the mirror stage, babies have poor control over their bodies; they may not be able to walk, have limited motor control and are dependent on others. In this sense, rather than seeming whole and unified, the child’s body seems to be fragmented.

The image in the mirror, on the other hand, is whole and unified. By identifying with the image, the child will also feel whole. This identification with the image is the formation of the ego. But the flipside of this process is that rather than identifying with their actual body, the child is identifying with an image of the body. This is an image which will always be outside of and separate from the body. Therefore, the formation of the ego is also an alienating process; the self does not coincide with the body, rather, it is an imaginary version of the self.