Gustave Fechner: Proof that the Moon consists of iodine (1821)

We have met Gustave Fechner before and we were not quite sure how seriously to take what he was saying. Similarly jesting appears to be his work Beweis, dass der Mond aus Iodine bestehe that actually appeared a year earlier than the panegyry to current medicine we have studied before. This time, it is not the whole of medicine that is the apparent topic of the writing, but the newly found habit of using iodine as a curative substance for almost any ailment. Fechner notes jestingly that even the most opposite medicinal schools use it, but just for opposite reasons: iodine has a tendency to lessen the fat of the people who eat it, thus, allopathics (those insisting that drugs should have opposite effects to the illnesses they are used for) can use iodine to cure obese people, while homeopathics (those insisting that drugs should have same effect to illnesses they are used for) can use it to cure the loss of body weight in tuberculosis.

If iodine is so useful a medicine, Fechner continues the joke, certainly it must be produced in great quantities, at least for the use of allopathic doctors (homeopathics require only very little of any medicine they use, he adds). Fechner makes the passing remark that if iodine is known to cure women who cannot menstruate, such women could be used to mine it, since they have an intrinsic ability to know where to find it. Then he notes that iodine was actually discovered by Bernard Courtois, when applying sulfuric acid to ashes of seaweed, which then let out a reddish cloud of iodine. This procedure did not produce that much of iodine, so certain practitioners of medicine had just assumed that anything with a similar reddish tinge might contain some iodine.

Fechner suggests going even further with this sort of deduction, and indeed, with a twinkle in his eye insists that the less a science is based on anything real, the more divine it certainly must be. With a clear reference to the Schellingian school of philosophy, he notes that any incompetent person can build a system empirically from what nature provides them, but only a genius can, as it were, construct the pyramid upside down, beginning from a single proposition and then working against the nature to show what the world must be really like in light of this proposition. Furthermore, Fechner emphasises, this axiomatic proposition need not even be proven, since it should be the basis of everything else.

Applying the hilarious suggestion how to construct systems to the question of iodine, Fechner begins with the known fact that iodine cures goitre and leaps to the conclusion that anything that cures goitre must contain iodine (surprisingly good conclusion of a joke, since goitre is effectively caused by a lack of iodine). Then he points out that often the same substances are used to cure both scrofula and goitre and deduces from this that iodine must also cure scrofula, and indeed, any substance used as a cure for scrofula must contain some iodine. Since the medicine of Fechner’s time applied many substances to either goitre or scrofula, they could be all lumped together as containing iodine – even the knives used for cutting the bumps caused by either goitre or scrofula.

Fechner isn’t satisfied with this, but wants to find an even bigger source of iodine and he discovers it in Moon, which, so the old wives tell us, can also cure goitre. Indeed, he adds, in this it resembles the seaweed, from which iodine was originally extracted, since the Moon is floating, as it were, in the ocean of universe. The old tales tell that the curative powers of the Moon are especially evident when it is waning, obviously because it is then spreading its iodine rays to Earth. 

Taking another stab at the Schellingian school, Fechner notes that the moon light cannot be proper light, which by the axiom of the philosophy of nature should also contain its opposite. According to Schellingians, this opposite is warmth, and with equally convincing analogies as Fechner, Schellingians had identified such things as egoism, lies, acidness, ganglias and plants as modifications of warmth, while virtue, truth, base, brains and animals corresponded then with light. Like these philosophers couldn't be virtuous without being somewhat vicious, Fechner jests, the proper light must also be warm, while the moon light must be something else, that is, iodine.

Fechner began by noting that people had tried to identify substances containing iodine through their reddish tinge. But isn't moon light yellow? Fechner borrows another phrase from Schellingians and suggests that the yellow colour is just another potency of the reddish iodine. Indeed, as a final quip, he notes that our skin can be coloured yellow with iodine and that the reddish tinge of the evening sky must be the effect of the iodine from the Moon.