Assagioli summarized his view of the human psychological constitution in the following diagram which has come to be called the “egg diagram”.

The area within the central circle is the field of consciousness, at the center of which is the “I” or personal self. The “I” is the point of pure awareness and will which is the subject of our field of consciousness and the integrating center of our personality. We can realize what is meant by the “I” if we step back to that place within us from which we can register and observe the various aspects of our experience. We can become aware, for example, that we are experiencing various sensations in our body, and that these sensations—the content of consciousness—are something different from the source or subject of consciousness. These sensations are constantly changing; they may be pleasant one moment and unpleasant the next. The observer, however—the one who is aware—remains the same. We can experience a center of stable identity within us which does not fluctuate with the changing contents of consciousness, with our momentary and transient experiences. Just as we can register awareness of our physical experiences, so we can register awareness of emotional and mental experience. If we observe our emotional states, we will realize that these too are constantly changing. One moment we are happy, the next moment we are sad. We may experience fear, anger, love, and joy all within the same day, but our center of identity, the Observer of these experiences, remains the same. In a similar way, we can observe the endless sequence of thoughts and images that flow by in our mind stream. Our mental life is full of movement; the mind finds it difficult to stand still for even a minute. Yet the “I” consciousness that underlies these experiences, remains the same. Like the projection screen on which a film plays, it provides us with a sense of permanence and stability in spite of the fact that the contents of our consciousness are ceaselessly in flux.

Returning to the “egg diagram”, it can be seen that the “I” or personal self is connected by a dotted line to a point above it—the higher or transpersonal Self. This transpersonal. Self, like the personal self, is a center of consciousness and of will with the difference that its domain is more inclusive. The transpersonal Self is able to extend its awareness to include the whole realm of the personal unconscious as well as the more limited field of consciousness. It is the center around which integration takes place at the stage of the transpersonal or spiritual psychosynthesis. Many people have had no direct conscious experience of their transpersonal Self, as this is something that generally comes in the more advanced stages of inner evolution. Assagioli’s inference of the existence of the transpersonal Self is based on the testimony of those who have experienced it. Reports have been given by the mystics who speak of a blissful, unitive experience of pure Being in which all polarities and contradictions seem to be resolved and which has a powerful integrating effect upon the personality (Bucke, 1923). Other persons who have practiced various psychological techniques such as mental imagery or meditation have reported similar experiences. We can also surmise the existence of a deeper center of identity within ourselves from the fact that the conscious “I” may disappear, as in sleep or under anesthesia, without causing us to loose the sense of continuity of our existence.