What does acausal connecting principle mean?

The phrase is Jung's technical name for a fourth explanatory principle — one that stands alongside space, time, and causality in accounting for how events in the world cohere. He introduced it formally in his 1952 essay Synchronicity: An Acausal Connecting Principle, though the idea had been gestating for decades. The name is deliberately paradoxical: a "principle" that "connects" without "causation." Understanding why Jung needed such a thing requires understanding what causality cannot do.

Classical physics, as Clarke (1994) summarizes it, conceived the world as a domain of material entities governed by immutable causal laws — every event explicable by reference to antecedent causes, which are themselves expressions of universal deterministic law. The problem Jung kept encountering, first in his own life and then repeatedly with patients, was a class of events that refused this framework: two occurrences, psychic and physical, that coincided in meaning without any traceable causal link between them. The scarab is the canonical example — a patient recounting a dream of a golden scarab while, at that precise moment, a scarab-like beetle knocked against the consulting-room window. No causal chain connects the dream to the insect. Yet the coincidence carried unmistakable meaning, and that meaning was therapeutically decisive.

Jung's move was to argue that meaning itself functions as a connective principle — not derived from causation, but coordinate with it. He formulated this most precisely in a letter to Pascual Jordan in 1934:

"The strange cases of parallelism in time, which are commonly called coincidences but which I call synchronistic phenomena, are very frequent in the observation of the unconscious."

And in his memorial address for Richard Wilhelm, he stated the positive claim directly:

"It seems as though time, far from being an abstraction, is a concrete continuum which possesses qualities or basic conditions capable of manifesting themselves simultaneously in different places by means of an acausal parallelism, such as we find, for instance, in the simultaneous occurrence of identical thoughts, symbols, or psychic states."

The word acausal is doing precise work here. Jung is not saying that synchronistic events are random or uncaused in some vague sense. He is saying that the connection between the two events — inner and outer — is not a causal connection. No energy is transmitted; no force propagates from one to the other. What links them is their shared meaning within a particular moment. The tertium comparationis — the third thing that makes comparison possible — is the archetypal pattern that both events express simultaneously.

This is why Jung, working with Wolfgang Pauli, eventually proposed a quaternary schema of explanatory principles: indestructible energy, the space-time continuum, causality, and synchronicity. Causality and synchronicity occupy opposite poles — one describes constant connection through effect, the other describes inconstant connection through contingence, equivalence, or meaning (Jung, 1960). Neither cancels the other; they are complementary.

Von Franz extended this framework by situating synchronicity within the broader concept of acausal orderedness — a more general principle of which synchronistic events are a special, perceptible case:

"I incline in fact to the view that synchronicity in the narrow sense is only a particular instance of general acausal orderedness — that, namely, of the equivalence of psychic and physical processes where the observer is in the fortunate position of being able to recognize the tertium comparationis."

The properties of natural numbers, the discontinuities of microphysics, the decay rates of radioactive elements — these are all instances of acausal orderedness that occur with regularity and can be studied experimentally. Synchronistic events proper are irregular, unrepeatable, and therefore statistically intractable; but they belong to the same family of phenomena.

The ontological ground for all of this is the unus mundus — the primordial psychophysical unity in which the distinction between psyche and matter has not yet been drawn. Synchronistic events are, on this account, eruptions of that unitary background into the differentiated world of consciousness: moments when the boundary between inner and outer becomes briefly permeable, and the underlying orderedness of things becomes legible.

What the acausal connecting principle ultimately names, then, is not an anomaly but a category of natural order — one that requires meaning, not mechanism, as its explanatory currency.

  • synchronicity — the acausal connecting principle, its ontological ground in the psychoid archetype, and its relation to the unus mundus
  • unus mundus — the primordial psychophysical unity that synchronicity presupposes
  • Marie-Louise von Franz — Jung's principal continuator on synchronicity, number, and acausal orderedness
  • Wolfgang Pauli — the physicist whose collaboration with Jung produced the quaternary schema of explanatory principles

Sources Cited

  • Jung, C.G., 1966, The Spirit in Man, Art, and Literature
  • Jung, C.G., 1960, The Structure and Dynamics of the Psyche
  • Jung, C.G., 1973, Letters Volume 1: 1906–1950
  • von Franz, Marie-Louise, 2014, Psyche and Matter
  • Clarke, J.J., 1994, Jung and Eastern Thought