Although the alchemists were more or less aware that their insights and truths were of divine origin, they knew they were not sacred revelations but were vouchsafed by individual inspiration or by the lumen naturae, sapientia Dei hidden in nature. The autonomy of their insights showed itself in the emancipation of science from the domination of faith. Human intolerance and shortsightedness are to blame for the open conflict that ultimately broke out between faith and knowledge. Conflict or comparison between incommensurables is impossible. The only possible attitude is one of mutual toleration, for neither can deprive the other of its validity. Existing religious beliefs have, besides their supernatural foundation, a basis in psychological facts whose existence is as valid as those of the empirical sciences. If this is not understood on one side or the other it makes no difference to the facts, for these exist whether man understands them or not, and whoever does not have the facts on his side will sooner or later have to pay the price.
With this I would like to conclude my remarks on sulphur. This arcane substance has provided occasion for some general reflections, which are not altogether fortuitous in that sulphur represents the active substance of the sun or, in psychological language, the motive factor in consciousness: on the one hand the will, which can best be regarded as a dynamism subordinated to consciousness, and on the other hand compulsion, an involuntary motivation or impulse ranging from mere interest to possession proper. The unconscious dynamism would correspond to sulphur, for compulsion is the great mystery of human life. It is the thwarting of our conscious will and of our reason by an inflammable element within us, appearing now as a consuming fire and now as life-giving warmth.
Carl Jung, Personification of the Opposites (Sulphur), Mysterium Conjunctionis