Homeopathy is not a coherent system but a loose collection of ideas, each of which is scientifically unsupported. The most important are the following two: The similia principle Homeopaths sometimes call this the 'Law of Similars'. The inventor of homeopathy, Samuel Hahnemann, may have believed that he'd discovered a natural law when he tested a widely-used malaria treatment — chinchona bark — on his own healthy person and decided that the symptoms he suffered as consequence were similar to those of malaria itself. But ideas of similarity are highly subjective and homeopaths sometimes disagree amongst themselves about which remedy is the true 'similimum' for the ailment in question. There is no scientific support for the notion that 'like treats like' as a general principle. Experiments conducted by Hahnemann for the purpose of establishing which substances produce which symptoms are scientifically worthless, not least because he used volunteers who knew what they were taking and what