My preoccupation with the psychology of the unconscious processes long ago compelled me to look about for another principle of explanation, because the causality principle seemed to me inadequate to explain certain remarkable phenomena of the psychology of the unconscious.
Many phenomena that happen in the world may be produced by a cause. A cause generates an effect. But there are others that show no cause. They simply happen.
Jung has introduced this concept of synchronicity to explain acasual phenomena, those that were not the result of a cause. They cannot be explained by a cause that preceded them.