Freud uses three distinct terms for the agency that propels the subject to act ethically:

“Freud uses three distinct terms for the agency that propels the subject to act ethically: he speaks of ideal ego (Idealich), ego-ideal (Ich-Ideal) and superego (Ueberich). He tends to identify these three terms: he often uses the expression Ichideal oder Idealich (Ego-Ideal or ideal ego), and the title of the chapter III of his booklet The Ego and the Id) is “Ego and Superego (Ego-Ideal)”. Lacan introduces a precise distinction between these three terms: the “ideal ego” stands for the idealized self-image of the subject (the way I would like to be, I would like others to see me); the Ego-Ideal is the agency whose gaze I try to impress with my ego image, the big Other who watches over me and propels me to give my best, the ideal I try to follow and actualize; and the superego is this same agency in its revengeful, sadistic, punishing, aspect. The underlying structuring principle of these three terms is clearly Lacan’s triad Imaginary-Symbolic-Real: ideal ego is imaginary, what Lacan calls the “small other,” the idealized double-image of my ego; Ego-Ideal is symbolic, the point of my symbolic identification, the point in the big Other from which I observe (and judge) myself; superego is real, the cruel and insatiable agency which bombards me with impossible demands and which mocks my failed attempts to meet them, the agency in the eyes of which I am all the more guilty, the more I try to suppress my “sinful” strivings and meet its demands. The old cynical Stalinist motto about the accused at the show trials who professed their innocence (“the more they are innocent, the more they deserve to be shot”) is superego at its purest.

What follows from these precise distinctions is that, for Lacan, superego “has nothing to do with moral conscience as far as its most obligatory demands are concerned”: superego is, on the contrary, the anti-ethical agency, the stigmatization of our ethical betrayal. So which one of the other two is the proper ethical agency? Should we – as some American psychoanalysts proposed, relying on a couple of Freud’s ambiguous formulations – set up the “good” (rational-moderate, caring) Ego-Ideal against the “bad” (irrational-excessive, cruel, anxiety-provoking) superego, trying to lead the patient to get rid of the “bad” superego and follow the “good” Ego-Ideal? Lacan opposes this easy way out – for him, the only proper agency is the fourth one missing in Freud’s list of the three, the one sometimes referred to by Lacan as “the law of desire,” the agency which tells you to act in conformity with your desire. The gap between this “law of desire” and Ego-Ideal (the network of social-symbolic norms and ideal that the subject internalizes in the course of his or her education) is crucial here. For Lacan, the seemingly benevolent agency of the Ego-Ideal which leads us to moral growth and maturity, forces us to betray the “law of desire” by way of adopting the “reasonable” demands of the existing socio-symbolic order. The superego, with its excessive feeling of guilt, is merely the necessary obverse of the Ego-Ideal: it exerts its unbearable pressure upon us on behalf of our betrayal of the “law of desire.” The guilt we experience under the superego pressure is not illusory but actual – “the only thing of which one can be guilty is of having given ground relative to one’s desire,” and the superego pressure demonstrates that we effectively are guilty of betraying our desire.”

― Slavoj Zizek, How To Read Lacan // Free delivery worldwide