Investigation of the psychology of the unconscious confronted me with facts which required the formulation of new concepts. One of these concepts is the self. The entity so denoted is not meant to take the place of the one that has always been known as the ego, but includes it in a supraordinate concept. We understand the ego as the complex factor to which all conscious contents are related. It forms, as it were, the centre of the field of consciousness; and, in so far as this comprises the empirical personality, the ego is the subject of all personal acts of consciousness. The relation of a psychic content to the ego forms the criterion of its consciousness, for no content can be conscious unless it is represented to a subject.
— Carl Gustav Jung
Jung is drawing a boundary here, and the boundary matters. The ego is not dismissed — it is the only engine of consciousness we have, the hinge on which any psychic content swings into awareness. What he is proposing is not its demotion but its relocation: from sovereign to tributary, from center of the personality to center of consciousness, which turns out to be a smaller room than we assumed.
The pressure in this passage is architectural. If no content can be conscious unless it is represented to a subject, then the ego's necessity is absolute and its sufficiency is zero. It must be present for anything to register; it cannot contain what generates it. That gap — between what the ego anchors and what the self exceeds — is not a spiritual promise. Jung is not telling you that something larger will redeem your suffering or gather your fragmentation into coherence. He is making a structural observation: the center you have been using to orient yourself is itself oriented by something it cannot fully see.
The self, in this early formulation, is a supraordinate concept before it becomes a living symbol — a logical container before it becomes the mandala, the filius philosophorum, the Christ-image that fills Aion's later chapters. Reading the definition without the chapters that follow it is reading the blueprint without the building.
Carl Gustav Jung·Aion: Researches into the Phenomenology of the Self·1951