To Edward Whitmont

Dear Colleague 4 March 1950

I have read your paper with great interest.

Your approach to the problem of psychophysical parallelism seems to me correct in all essentials, so far as I can judge this from the psychological side.

The difficulty this problem comes up against is that what we can grasp psychologically never goes deep enough for us to recognize its connection with the physical.

And conversely, what we know physiologically is not sufficiently advanced for us to recognize what would form the bridge to the psychological.

If we approach from the psychological side we come up against the phenomena I have termed archetypes.

If I am not mistaken, these irrepresentable formations, in their whole mode of action, correspond to the “patterns of behaviour” in biology, since they seem to represent the basic forms of psychic behaviour in general.

To know what these forms are in themselves, we would have to be able to penetrate into the whole mystery of the psyche.

But this is totally unconscious to us, because the psyche cannot lay itself by the heels.

We can do no more than carefully tap out the phenomenology that gives us indirect news of the essence of the psyche.

Similarly-from the other side-physics is tapping its way into irrepresentable territory which it can visualize only indirectly by means of models.

Both sciences, the psychology of the unconscious and atomic physics, are arriving at concepts which show remarkable points of agreement.

Here I will mention only the concept of complementarity.

If we consider the psyche as a whole, we come to the conclusion that the unconscious psyche likewise exists in a space-time continuum, where time is no longer time and space no longer space.

Accordingly, causality ceases too.

Physics has reached the same frontier.

Since the one line of research proceeds from within outwards and the other from without inwards, and there is no hope of our reaching the point where the two meet, there is nothing for it but to try to find points of comparison between the deepest insights on both sides.

But this is where the above-mentioned difficulty comes in: our knowledge of the instincts, i .e., of the underlying biological drives, is very inadequate, so that it is only with the greatest difficulty and great uncertainty that we can equate the archetypes with them.

And when it comes to the chemistry of albumen, in my view all possibilities of comparison cease altogether.

There is, however, another possibility that should not be lost sight of, and that is synchronicity, which is basically nothing other than correspondentia more specifically and more precisely understood, and was as we know one of the elements in the medieval explanation of the world.

It is conceivable-and there are facts pointing in this direction-that an archetypal situation will reflect itself also in physical processes.

Thus, as early as the dream-book of Artemidorus, we come across the case of a man dreaming that his father perished in a fire, and after a few days the dreamer himself died of a high fever.

I have observed such things.

These correspondences can go still further and give rise to the most curious meaningful coincidences.

This question could be answered more or less satisfactorily only if the dreams of physically ill persons were systematically investigated.

One might then be able to see what dream motifs correspond to what physical states.

But no investigations of the sort have yet been made.

Your approach is somewhat along these lines.

As you know, these ideas were brought to a high pitch of development by Paracelsus.

Today it is a question of finding conclusive proofs.

If one wants to work this field, one encounters the further difficulty that the statistical method of science, which alone furnishes adequate proofs, stands in a relationship of complementarity to synchronicity.

This means that when we observe statistically we eliminate the synchronicity phenomenon, and conversely, when we establish synchronicity we must abandon the statistical method.

Nevertheless, the possibility remains of collecting a series of individual instances of correspondence, each instance throwing its own light on the phenomenon of synchronicity.

It would be conceivable, for instance, that salt has a general biological significance and efficacy which correspond in some way to the symbolic significance of salt.

But this constellation could be substantiated only by a large number of individual observations.

I think this would be a very difficult undertaking as long as we know so little about the nature of synchronicity, which, incidentally, has nothing to do with synchronism but connotes a meaningful coincidence which is not necessarily synchronism in the strict sense.

With collegial regards,

Yours sincerely,

C.G. Jung Carl Jung, Letters Vol. 1, Pages 546-548.