This paper is Glover's contribution to the symposium on Ego Strength and Ego Weakness, held at the International Psychoanalytic Congress at Paris in 1938. Glover stresses the fact that the concept of ego strength cannot be comprehended from one angle alone. Dynamic, economic and structural criteria must be applied simultaneously. Dynamically, an optimal freedom from anxiety and from guilt-arousing and energy-consuming defenses is the premise for a good mastery of instincts as well as of affects. Economically, the capacity for harmonious adaptation through an efficient application of the mechanisms of displacement is the most essential factor.

The structural point of view is discussed by Glover at greater length. He repeats and discusses his well-known thesis of a multilocular origin of the ego, composed of derivatives of various 'ego nuclei' which came into being independently of each other from the struggles between component instincts