To Hans Bender
Dear Colleague, 6 March 1958
I have looked through the galleys as requested.
I quite agree with you that the word "effect" should really always be put in quotation marks or, better, avoided altogether.
Everything that can be repeated experimentally is necessarily causal, for the whole concept of causality is based on this statistical result.
If, for instance, we examine Rhine's experiments critically,we cannot avoid the conclusion that they include a causal factor in so far as they are repeatable.
We think this causal factor is to be found in the known emotional condition, i.e., in the archetypal situation.
The experimental activation of an archetypal situation has to be explained causally, since there is no possibility of explaining it otherwise and no reason to do so.
In this emotional condition a syndrome occurs which has no causal explanation, but it does not occur of necessity and does not occur regularly, only with a certain frequency that exceeds mere probability.
How it comes about that space and time are reduced by these meaningful chance occurrences cannot be understood in terms of causality.
This is most obviously the case with precognitions.
If we succeed in producing an archetypal situation experimentally, we create an opportunity for such occurrences to produce themselves, though they need not.
According to Leibniz and Schopenhauer these lateral connections of events are necessary events, i.e., they must occur under certain conditions.
But this is not borne out by experience.
Nevertheless, Rhine's experiments prove that their probability is lower than the mathematical probability.
The situation is undoubtedly complicated and at every step one risks falling back into the causal view again.
There is also-and this point must always be kept in mind-the possibility of certain physical factors which we simply know nothing about at present.
In the existing state of our knowledge, anyway, it seems utterly Impossible to reverse causality, as in precognition, where a future event, apparently not yet in existence, causes an event in the present.
Even so it should be noted that Heisenberg considers a reversal of the time flow in the microcosm thinkable.
The microcosm, however, coincides with the unconscious.
The hypothesis of a fabric of order would fit the Leibniz-Schopenhauer Theory perfectly, according to which correspondences must occur at the points of intersection between the meridians and the parallels.
But for this, as I have said, there is no evidence.
Everything, at least so far as my experience goes, indicates that undeniable correspondences do occasionally occur, which I call "synchronistic" just because of their temporal simultaneity, i.e., their coincidentia.
With regard to the horoscope I have serious doubts whether it can be understood as a purely synchronistic phenomenon, for there are unquestionable causal connections between the planetary aspects and the powerful effects of proton radiation, though we are still very much in the dark as to what its physiological effects might be.
Regarding my secretary's letter I would like expressly to authorize the publication of my first letter as well as any use you might care to make of this one.
C.G. Jung ~Carl Jung, Letters Vol. II, Pages 420-421