Id's counterpart

EGO

In Freud's model of the psyche, this rational mediator balances the impulsive desires of the id with the moral constraints of the superego.

This clue refers to Sigmund Freud’s psychoanalytic theory, where the "id" is the instinctual, unconscious part of the mind. Its counterpart is the "ego," which mediates between the id’s impulses and reality. The answer plays on the direct opposition implied by "counterpart," making "EGO" the logical fit. No wordplay here—just a straightforward nod to classic psychology.