[Samuel Hahnemann and the principle of similars].

The principle of similars (treat likes by likes) is generally considered to be one of the pillars of the homeopathic doctrine established by Samuel Hahnemann (1755-1843). Nevertheless, its status and relevance with regard to the practice of homeopathy can be challenged by semantic, conceptual, and epistemological objections. 1. Contrary to its literal meaning, "similia similibus curentur" is commonly used in the sense of "all diseases should be treated by similar drug diseases", thus transgressing its original field of indication. 2. From 1796, when Hahnemann published his first definition of the principle of similars, he gradually raised his claims from merely suggesting a heuristic principle for finding new curative remedies to insisting on having discovered a law of nature and the only true way of healing, in 1807/1808. To substantiate his ambitious tenets, Hahnemann had to introduce a variety of theories which in turn were to become the main battleground in the ensuing controversy about homeopathy. 3. From the perspective of epistemology of science, science can never consist of a final set of absolute truths or the like but must rather be described as a continuous social process that retains a methodological cycle of abduction, deduction, and induction. From the perspective of theory of medicine, however, medicine is to be considered as a practical rather than a cognitive science in its own right. Its first concern ought to be the development of practical directions for treating patients, while the value of competing theories can only be judged from their usefulness in practice. Hence, even though Hahnemann's theories, including his conception of the principle of similars, may be untenable or outdated, the genuine method of homeopathic treatment he founded remains independent of and unaffected by criticism at the level of theory and concepts.