(Liminalities, Cycle 1, Part 1)
A seminal moment in the formation of Carl Jung’s concept of synchronicity came as he was treating a highly educated woman who, by his description, was locked in a rigid Cartesian rationalism that hindered her therapy. The basis of all depth psychotherapy is the airing of unconscious psychic content and its integration with the conscious sense of self, but this woman was centered in a view of reality that denied the existence or significance of such things and kept her wholly imprisoned in her rational ego.
One day as they sat together in Jung’s office, the woman told him of a dream from the previous night in which she was given a golden scarab beetle. As an iconic symbol of death and transformation in ancient Egypt, the scarab is a symbol resonant with psychological meanings, as Jung was well aware. But the situation quickly transcended the realm of purely abstract symbolism when Jung heard a gentle, insistent tapping on the window behind him. As he later recounted,
I turned round and saw a fairly large flying insect that was knocking against the window-pane from outside in the obvious attempt to get into the dark room. That seemed to me very strange. I opened the window immediately and caught the insect in the air as it flew in. It was a scarabaeid beetle, or common rose-chafer (Cetonia aurata), whose gold-green colour most nearly resembles that of a golden scarab. I handed the beetle to my patient with the words, “Here is your scarab.” The experience punctured the desired hole in her rationalism and broke the ice of her intellectual resistance. The treatment could now be continued with satisfactory results. 
This event became the chief instance that Jung regularly referred to as an illustration of synchronicity in action.