Synchronicity is not a philosophical view but an empirical concept which postulates an intellectually necessary principle. This cannot be called either materialism or metaphysics. No serious investigator would assert that the nature of what is observed to exist, and of that which observes, namely the psyche, are known and recognized quantities. If the latest conclusions of science are coming nearer and nearer to a unitary idea of being, characterized by spate and time on the one hand and by causality and synchronicity on the other, that has nothing to do with materialism. Rather it seems to show that there is some possibility of getting rid of the incommensurability between the observed 'and the observer. The result, in that case, would be a unity of being which would have to be expressed in terms of a new conceptual language-a "neutral language," as W. Pauli once called it.
— Carl Gustav Jung
Jung is not announcing a discovery here — he is naming a problem in the instruments of observation. The observer and the observed have never sat comfortably on opposite sides of the table, and every discipline that has tried to enforce that separation has eventually had to account for the table itself. What synchronicity forces into view is that the psyche is not a window onto events but a participant in them, which means the usual appeals to objectivity — the scientist's apatheia, the analyst's neutrality — are already implicated in what they claim to measure.
The phrase "neutral language" is worth sitting with. Pauli meant something precise by it: a symbolic register that would neither reduce inner events to physical substrate nor dissolve matter into mental projection, but would let both cohere in a single descriptive act. Jung took the invitation seriously because he had encountered, repeatedly, events that refused the causal register entirely — moments where meaning cohered across a gap no force could bridge. His response was not mystical assertion but methodological: if the data keep exceeding the instrument, build a better instrument, or at least name the one you are already using. What he is proposing here is not a metaphysics of cosmic connectedness. He is proposing honesty about the limit of the frame.
Carl Gustav Jung·The Structure and Dynamics of the Psyche·1960