The great breakthrough, which put an end to the dualism of psyche and matter, was achieved by Jung in his work on synchronicity. It is by no means a chance event that synchronicity has to do with the problem of time, because time is, for the physicist also, an unresolved problem. Mirrorsymmetry versus asymmetry, time-reversibility versus directed linear time (according to the second thermodynamic law), are still problems discussed in microphysics. It is just at this point that Jung's investigations in the realm of the objective psyche come to meet the physicists-in that marginal realm of the psychoid archetype, where activated or excited archetypes simultaneously manifest themselves in inner and outer reality, either in direct identity or in a symbolic identity of meaning. Time then appears no longer as an empty frame of reference, in which events take place, but as a qualitatively characterized stream of events. In his investigation of synchronistic phenomena, Jung made a further important distinction, namely between the regular eternal or timeless aspect of the principle of synchronicity (which he called acausal, or a priori, orderedness) and irregularly occurring spontaneous synchronistic events. The latter point to an active, even arbitrary, ordering of the transcendental background of existence, or to, as he puts it, a continuous creation. In another context, Jung termed this background of existence the unus mundus
— Marie-Louise von Franz
Jung's synchronicity argument does something genuinely strange to the question of time: it refuses to let time remain a neutral container. The physicist's embarrassment — why does entropy give time a direction that the equations themselves do not require? — and the analyst's embarrassment — why does this dream arrive the night before the phone call? — turn out to share a border. Von Franz is pointing at that border, not decorating it.
What makes the passage worth sitting with is the distinction she draws near the end, the one that is easiest to pass over. Jung separates the timeless principle of acausal orderedness — a kind of background grammar of meaning — from the irregularly occurring event in which that grammar suddenly fires. The first is abstract, even theological; the second is what actually hits you. A synchronicity lands because it is spontaneous and uninvited, because you did not summon it through sufficient attentiveness or spiritual preparation. That uninvited quality is the whole point. The soul is not rewarded for effort here; it is interrupted. Whatever logic was running — that if you understood deeply enough, or prepared carefully enough, you would finally secure some footing — the synchronistic event ignores it entirely. The unus mundus does not respond to readiness. It arrives in its own time, which is to say: in no time you arranged.
Marie-Louise von Franz·Psyche and Matter·2014