As infant (mouth) and mother (breast) are not identical, or better, not one whole, any longer, a libidinal flow between infant and mother originates, in an urge towards re-establishing the original unity. It is this process in which consists the beginning constitution of a libidinal object. The emancipation from the mother, which entails the tension system between child and mother and the constitution of libidinal forces directed towards her, as well as of libidinal forces on the part of the mother toward the child – this emancipation and tension culminate in the phallic phase of the psychosexual development, lead to the Oedipus situation, and to the emergence of the super-ego.
The development away from primary narcissism, that is, the development of the ego, culminates in the resolution of the Oedipus conflict through the castration complex. The castration threat, directed against the gratification of libidinal urges toward the mother so that she is given up as a libidinal object, is seen as the representative of the demands of reality, and the submission to the castration threat as the decisive step in the establishment of the ego as based on the reality principle.
Hans Loewald – The Essential Loewald: Ego and Reality p.6
The Sea Is Not Full 