The failure to remember previous incarnations will be more clearly understood if we now give some thought to the fact that the personality here on the material plane is only a fragment of the whole consciousness of the soul. As we come down into lower planes from the mental world each grosser grade of matter through which the ego expresses itself is a limitation of consciousness. On the astral plane each of us, whatever he may be here, is more alive and enjoys an actual extension of consciousness. On the mental plane he has enormously greater wisdom than here, with a still further extension of consciousness that is quite beyond the present comprehension of the brain intelligence.
To put it differently, the ego really does not come into incarnation at all. It merely sends outward a ray from itself--a mere fragment of itself, as a man might put his hand down into the water of a shallow stream to gather bits of ore from which gold can be obtained. So the ego puts a finger, only, down into denser matter to get the general experience that can be transmuted into the gold of wisdom and skill. That finger of the ego, that we know as the personality, gathers the experience and then it is withdrawn into the ego. During the incarnation the personality has been animated by only a little of the ego's vast intelligence and that is why it blunders so often. But, veiled in dense matter, not much of the ego's consciousness can reach it.
The relationship between the ego and the personality may be illustrated by that which exists between the brain consciousness and that of the finger-tip. The difference, of course, is great. The finger tip cannot see of hear or taste or smell. It is limited to one sense--touch. But it is a form of consciousness, and it can get experience and pass it on to the brain consciousness. A man may be addressing an audience and see some substance on the table before him. It may be sand or sugar. Without interrupting his lecture he can put down his finger and get at the truth about the matter. The finger-tip gets the information and passes it on to the brain consciousness. Meantime there has been no pause in the discourse. Not a phrase nor a word nor the shading of a thought has been missed. The intellectual life went on in its completeness while the ray of intelligence sent down in the finger-tip got and reported the fact as it was. Just so the life of the ego--the true self of each of us--goes forward on its home plane while the personality here gropes for its harvest of experience. Some of those experiences will be painful to the personality, and the event will seem tragic here, but it will be a passing incident to the ego. In the illustration just used the substance on the table may prove to be neither sand nor sugar, but tiny bits of glass. Some of the sharp points may penetrate the finger and pain follows. To the finger-tip consciousness it is a blinding flash of distress that is overwhelming. But to the brain consciousness it is a trivial incident. And thus it is with most of our painful experiences here. They do a useful work in our evolution and they are trifling incidents to the consciousness of the ego.