Astrology is of particular interest to the psychologist, since it contains a sort of psychological experience which we call ‘projected’- this means that we find the psychological facts as it were in the constellations. This originally gave rise to the idea that these factors derive from the stars, whereas they are merely in a relation of synchronicity with them. I admit that this is a very curious fact which throws a peculiar light on the structure of the human mind.
Source:Letter to B.V. Raman (September 6, 1947), Letters, vol. 1, pp. 476-6