Paracelsus (1493?-1541) was one of the most remarkable figures in medicine. He firmly opposed the humoral theory of disease championed by Galen. He was first to write on miners' diseases, to establish the relationship between cretinism and endemic goiter and to note the geographic differences in disease.
Osler said that Paracelsus was "the Luther of medicine, for when authority was paramount he stood for independent study." Paracelsus believed the physician should know the following things:
The physician should know what is useful and what is harmful to unfeeling creatures to sea monsters and fish: what is pleasing and what is hateful to animals bereft of reason; what is healthy for them and what is unhealthy. This is what we must learn about Nature. What else? The powers of magic formulas, their origin and source, their nature: who is Melusina; who the Siren is; what is permutation, transplantation and transmutation; how to grasp them and how to understand them perfectly; what surpasses nature, species, life; the nature of the visible and of the invisible, of sweet and bitter; what has a good taste; what death is; what is used by the fisherman, the leather-worker, the tanner, the dyer, the blacksmith, the wood carver; what goes into the kitchen, in the cellar, in the garden; what concerns weather, the hunter's art and the miner's trade; the life of the vagabond and the homelover, the needs of the countryside and the causes of peace; the interests of the layman and the cleric; the occupations and the nature of different states, their origin; the nature of God and of Satan, poison and antidote, feminine nature and masculine nature; the difference between women and maidens, between yellow and buff; what is white, black, scarlet and grey; the reason for multiplicity of colours, for short and for long, for success and for failure; and how to obtain all these results.1