To H. Rossteutscher
Dear Herr Rossteutscher, 3 May 1958
Your reflections are eminently philosophical.
I myself do not belong to this fraternity, being a mere empiricist who is content with makeshift models.
But I do expect such a model to take adequate account of the nature of the phenomenon in question.
One characteristic that leaps to the eye is the absence of any demonstrable causation, or rather the impossibility of a causal hypothesis.
Hence the concept of “effect” falls to the ground, and its place is taken by the simple postulate of coincidence, which need not in itself have any causal connotation.
A second characteristic is the equivalence of meaning, which Gives mere coincidence the appearance of an interconnection.
Accordingly I chose the name synchronicity, as it brings out the relative simultaneity of such phenomena and supplements it with the conjecture of meaningful coincidence.
As you see, my hypothesis is not an explanation but only a designation.
It does however take due account of the fact that causality is a statistical truth which necessarily allows for exceptions.
The term “synchronicity” is first and foremost a proposed name which at the same time stresses the empirical fact of meaningful coincidence.
For the empiricist it is only a makeshift model, but it does not rule out the possibility of other hypotheses such as your “reciprocal effect.”
I would object at most to the term “effect” since it carries a causal flavour.
I am ready at any time to accept the idea of a reciprocal effect if anyone can demonstrate by empirical methods how this effect comes about.
You mention the archetype as a basis, and as a matter of fact an archetypal basis can be demonstrated in most cases of meaningful coincidence.
But no causal nexus is thereby expressed, since from what we know of the archetype it is a psychoid content which cannot with certainty be said to exert a simultaneous effect on external events.
We have only a very remote conjecture that psychic patterns fall in with the fundamental forms of the physical process in general. (“Psychoid” archetype!)
But this is a possibility that must remain open.
C.G. Jung ~Carl Jung, Letters Vol. II, Pages 436-437