The purely psychological interpretation only apprehends half of the matter. The other half is the revealing of the archetypal basis of the terms actually applied in modern physics. What the final method of observation must see in the production of "background physics" through the unconscious of modern man is a directing of objective toward a future description of nature that uniformly comprises physis and psyche, a form of description that at the moment we are experiencing only in a prescientific phase. To achieve such a uniform description of nature, it appears to be essential to have recourse to the archetypal background of the scientific terms and concepts.

Letter to Carl Jung, (16 June 1948)