The Doctrine of Signatures is a metaphysical method of discovering pharmaceutical value. Meanings are assigned to a given characteristic of a plant which then allow the herbalist to recall the element when a cure requires that meaning. This totemism of analysis has been very common as of three hundred years ago and continues to be upheld by many individuals. William Coles found that walnuts were good for curing head ailments because
they Have the perfect Signatures of the Head… and The little holes whereof the leaves of Saint Johns wort are full, doe resemble all the pores of the skin and therefore it is profitable for all hurts and wounds that can happen thereunto.
The Doctrine of Signatures is a very old notion which predates homeopathy and was already mentioned in the writings of the Swiss physician Paracelsus von Hohenheim (1493-1541). It proposes the idea that God gave everything in nature its unique healing powers and left a clue for us to discover in the appearance of each plant or substance. For example, the dark lines on the petals of Digitalis purpurea are reminiscent of blood vessels. Indeed, Digitalis is a well-known allopathic drug for heart problems and also has an affinity for this organ in its homeopathic preparation. Similarly, the yellow juice of Chelidonium majus reminds one of the yellowish complexion typical of patients with liver problems. Chelidonium is known for its affinity to the liver.
It was popularized in the early 1600s through the writings of Jakob Böhme (1575-1624), a master shoemaker in the small town of Görlitz, Germany. At the age of 25, Böhme had a profound mystical vision in which he saw the relationship between God and man. As a result he wrote Signatura Rerum; The Signature of all Things which espoused a spiritual philosophy but was soon adopted to medicine. Similar beliefs have been held in other cultures such as Native Americans, Asian, and even the people of the Appalachian region.
The remedy Pulmo vulpis was introduced by the homeopath Grauvogl, who, acting according to the law of Signatura Rerum recommended Pulmo vulpis in asthma because foxes were long-winded.
The Doctrine of Signatures has been derided and said to rest upon pure fancy; but I know of no accidents in nature and everything has an adequate cause, hence we should not be too ready to attribute such things to mere coincidence. Such correspondences are too numerous as well as much too striking to be lightly passed over. It seems rather a case of not knowing just what they mean or what the real connection is.
– C. M. Boger