But, of course, advice (or anything else) that is ‘based upon real and contemporary considerations’ must be a function of the part of the mind whose function it is to determine what is real and contemporary, namely, the ego.
If we look at the relationship between patient and analyst from the point of view of group psychology, the mutative interpretation consists of the analyst detaching himself from the basic-assumption group that he has joined with the patient (through mutual projective identification), and forming a work group. In terms of the psychology of the individual, it is the analyst detaching himself from a state of mind dominated by his archaic superego, and instead employing his ego - his capacity to simply observe what is real and contemporary in the psychic sphere.
Clinically, the analyst uses his ego to maintain contact with the patient's state of mind using his countertransference and other means. He then tries to convey to the patient what his state of mind is, or, rather, those aspects of it of which the patient is unaware. He does this without any implication about how the patient should be (which would be a superegoactivity encouraging splitting), but only tries to describe how, in the analyst's opinion, he actually is (an ego activity encouraging integration).
I believe that it would clarify our understanding of mutative interpretation if we did not follow Strachey in regarding the analyst as an ‘auxiliary superego’ for the patient. The analyst's work in mainly directed toward using his ego to place himself in a world different from that of the superego, one of impartial assessment of reality, without any of the moralistic disapproval or approval that is the essence of the world of the archaic superego. I believe that the reason that the mutative interpretation has its specific effect on the patient is not that the analyst turns out to be an ‘auxiliary superego’ for the patient, i.e. a better superego than the one the patient already has - but that he turns out to be an auxiliary ego, which is no kind of superego at all.
For this reason I believe it would deepen our understanding of the specific therapeutic action of psychoanalysis, and help us clarify the differences between psychoanalytic development and psychotherapeutic change, if we did not follow Strachey in regarding the analyst as an ‘auxiliary superego’ for the patient. In making a mutative interpretation, the analyst is acting as an ego, an agent of reality. The reality that he supports in the analysis is the clarification of who is who, what belongs to the patient and what to the analyst. By so doing, he incurs the hostility of the archaic superego, both the patient's and his own, the force of which is directed against an integrated view of reality and toward splitting, projection and confusion. Strachey wrote that in making a mutative interpretation, the analyst is testing his relationship to his own unconscious impulses. I believe, rather, that the mutative interpretation tests his relationship to reality, on one hand, and to his own archaic superego, on the other. For this reason, a successful mutative interpretation is therapeutic for the analyst as well as for the patient." (pp. 99-100)
Robert Caper (1995). On The Difficulty Of Making A Mutative Interpretation. International Journal of Psycho-Analysis, Vol. 76, pp. 91-101