In the final analysis the idea of an unus mundus [one world] is founded, on the assumption that the multiplicity of the empirical world rests on an underlying unity … . Everything divided and different belongs to one and the same world …. ~Carl Jung, CW 14, pars. 767-770

I think you are correct in assuming that synchronicity, though in practice a relatively rare phenomenon, is an all-pervading factor or principle in the universe, i.e., in the Unus Mundus, where there is no incommensurability between so-called matter and so-called psyche. ~Carl Jung, Letters Vol. II, Pages 398-400

Only numinous experiences retain their original simplicity or oneness which still gives us intimations of the Unus Mundus. ~Carl Jung, Letters Vol. II, Page 508-509

As Prof. Fierz in his speech at Pauli’s funeral has mentioned: Speculation comes from speculum. Thus “speculation,” a very typical form of consciousness, becomes the real centre of the world, the basis of the Unus Mundus. ~Carl Jung, Letters Vol. II, Pages 469-471