The hierosgamos is not a metaphor that got applied to chemistry — it ran through both registers simultaneously, which is precisely why the alchemists could not always say which they were doing. When the king and queen descend into the bath in the Rosarium series, the figures are philosophical, chemical, and erotic in the same instant. Von Franz is noting the continuity of that ambiguity into Jung's own reading: "The Psychology of the Transference" uses the same Rosarium woodcuts to think about what happens between analyst and patient, and the claim is not that this resembles sacred marriage but that the same psychic logic is at work across all three registers.

What that logic is: the soul moves toward wholeness through conjunction, and conjunction requires that the opposites remain genuinely opposite long enough to actually meet. The hierosgamos is not a merger that dissolves tension — it is a tension held to the point of transformation. This is where the alchemists were more precise than the language of unity usually is. The *coniunctio* they sought was the production of something that had not existed before, the *filius philosophorum*, which is not either parent and is not a compromise between them. That insistence — on the third that is neither — is what makes Mysterium Coniunctionis difficult and worth the difficulty.