The psychological union of opposites is an intuitive idea which covers the phenomenology of this process.
It is not an “explanatory” hypothesis for something that, by definition, transcends our powers of conception.
For, when we say that conscious and unconscious unite, we are saying in effect that this process is inconceivable.
The unconscious is unconscious and therefore can neither be grasped nor conceived.
The union of opposites is a trans-conscious process and, in principle, not amenable to scientific explanation.
The marriage must remain the “mystery of the queen,” the secret of the art, of which the Rosarium reports King Solomon as saying:
This is my daughter, for whose sake men say that the Queen of the South came out of the east, like the rising dawn, in order to hear, understand, and behold the wisdom of Solomon. Power, honour, strength, and dominion are given into her hand; she wears the royal crown of seven glittering stars, like a bride adorned for her husband, and on her robe is written in golden lettering, in Greek, Arabic, and Latin: “I am the only daughter of the wise, utterly unknown to the foolish.”
The Queen of Sheba, Wisdom, the royal art, and the “daughter of the philosophers” are all so interfused that the underlying psychologem clearly emerges: the art is queen of the alchemist’s heart, she is at once his mother, his daughter, and his beloved, and in his art and its allegories the drama of his own soul, his individuation process, is played out. ~Carl Jung, Psychology and Alchemy, Page 381.
Image: Medieval depiction of the Queen of Sheba from Prague, Bohemia