Freud's later work on ego psychology is discussed, in terms of its impact on psycho-analytic theory and practice. The revisions Freud and others have made are far from complete, but contain a series of attempts at useful formulations. Child observation and work on the mechanisms of defence have made large contributions. Future development is hard to predict.

An idea which the author considers throws light on many aspects of child development, and is common both to Freud's hypotheses and those of H. Hartmann, is that early stages of development can be described in terms of growing distance between ego and id. Our knowledge here remains comparatively primitive, despite the vast amount of work done, to which many references are given.