On the interplay between evidence and theory: Dr. Hahnemann's homeopathic medicine.

The focus of this paper is the interplay between evidence and theory, which is at the heart of the methodological question. I address it using as a case study the homeopathic medicine discovered/invented by C.S. Hahnemann in the late eighteenth century. After presenting a quick reconstruction of Hahnemann' s life and work as a medical doctor, I turn to the way in which he came to enunciate the two founding principles of homeopathy: the "law of simile" and the "law of dilution." I compare the way in which homeopathy was received and its therapeutic success evaluated up until the mid-to-late 1800s, to the way in which it is currently regarded. I conclude that the shift from a mixture of appreciation and doubt to the outright denial of all evidence in favour of homeopathy is in line with the most striking (though not necessarily the most productive) trend of twentieth century science: one that is heavily biased in favour of theory and against evidence. In the case of homeopathy such a position led to ignoring evidence gathered in diverse fields, mainly immunology and chemical physics, showing respectively that ultra-diluted solutions have biological effects and that the values of their parameters differ from those of water. The advancement of knowledge is more likely to result from a further investigation of this evidence, with the aim of explaining the law of dilution, than it is from insisting that this law is nonsense because an explanation of it is not, at present, available.