The imago of the counterpart is interchangeable with the image of the subject's own body, the specular image with which the subject identifies in the mirror stage, leading to the formation of the ego.
The image of another person's body can only be identified with insofar as it is perceived as similar to one's own body, and conversely the counterpart is only recognised as a separate, identifiable ego by projecting one's own ego onto him.
The counterpart is the little other because it is not truly other at all; it is not the radical alterity represented by the Other, but the other insofar as he is similar to the ego (hence the interchangeability of a and a' in schema L).
- Lacan, 1938: 35-9
counterpart 278 Seminar XI