The ego is formed out of identifications taking the place of abandoned cathexes by the id. The super- egos relation to the later alterations of the ego is roughly similar to that of the primary sexual phase of childhood to later life after puberty. As the child was once under a compulsion to obey its parents, so the ego submits to the categorical imperative of its super-ego. But the derivation of the super-ego from the Oedipus complex means that the super-ego is always close to the id and can act as its representative vis-à-vis the ego. Freud looks at these relations as they can be seen in clinical situations - such as 'negative therapeutic reactions', and the role of a conscious sense of guilt in both obsessional neuroses and melancholia. In all these situations the super-ego displays its independence of the conscious ego and its intimate relations with the unconscious id. The main question though, is, how the super-ego manifests itself as a sense of guilt and develops such extraordinary harshness and severity towards the ego (in these neuroses).
From the point of view of instinctual control - of morality - it can be seen that the id is totally non-moral, the ego strives to be moral and the super-ego can be super-moral and can then become as cruel as only the id can be.
Thus ideas about the ego get clearer. It has strengths and weaknesses and is entrusted with important functions. By virtue of its relation to the perceptual system it gives mental processes an order in time and submits them to 'reality testing'. By interacting with the processes of thinking, it secures a postponement of motor discharges and controls the access to motility. All the experiences of life originating from without, enrich the ego, the id, however is its second external world, which it strives to bring into subjection to itself. It withdraws libido from the id and transforms the object-cathexes of the id into ego-structures. With the aid of the super-ego, it draws from the experiences of past ages stored in the id.
There are two paths by which the contents of the id can penetrate into the ego. One is direct, the other leads by way of the ego-ideal, the path taken by any mental activity can though, be of decisive importance.
Equally, though we can see the ego as a poor concept, owing service to three masters and consequently menaced by three dangers, from the external world, from the id and from the severity of the super-ego. Three kinds of anxiety then correspond to these three dangers, the ego being the actual seat of anxiety, it withdraws its own cathexis from the id or the menacing perception - in both cases the fear being ultimately of death. The ego's fear of the super-ego, though, hides a fear of the conscience.
The ego is not impartial in its attitude towards the two classes of instincts. Through its work of identification and sublimation it gives the death instincts in the id assistance in gaining control over the libido (in doing so, though, runs the risk of becoming the object of the death instincts and perishing itself). In order to do this though, it must become filled with libido, and sexual instincts, desiring to live and be loved.
Finally, of these dependent relationships in which the ego stands, that to the super-ego is perhaps the most interesting, since the id has no means of showing the ego either love or hate, with Eros and the death instinct struggling within it, so the part played by these factors must not be underestimated.