Consider the snakes as they wind around the staff of Mercury. They are in eternal conflict. They represent  the opposites that can be perceived. Life & Death. Science & Art. Any pair of opposites you can imagine. They cannot unite at their own level, as Jung described because they are in eternal conflict. But provided enough energy and focus, a transcendent third may appear, represented by the winged globe above. This is wholeness, or the synthesis which arises from thesis and antithesis.