I have done a terrible thing, I have postulated a particle that cannot be detected. - Wolfgang Pauli

When that amusing "Pauli effect" of the overturned vase occurred, on the occasion of the founding of the Jung Institute, I had the immediate and vivid impression that I should "pour out water inside" (— to use the symbolic language that I have acquired from you). Then when the connection between psychology and physics took up a relatively large part of your talk, it became even more clear to me what I was to do. The outcome of all this is the enclosed essay.

Already in my original paper I stressed the circumstance that I was unable to give a logical reason for the exclusion principle or to deduce it from more general assumptions. I had always the feeling, and I still have it today, that this is a deficiency.

The designation "Jungian Psychology" is actually already unscientific sectarianism. I only acknowledge C. G. Jung's contribution to the general psychology of the unconscious.