Samuel Hahnemann

Every effective drug provokes in the human body a sort of disease of its own, and the stronger the drug, the more characteristic, and the more marked and more violent the disease. We should imitate nature, which sometimes cures a chronic affliction with another supervening disease, and prescribe for the illness we wish to cure, especially if chronic, a drug with power to provoke another, artificial disease, as similar as possible, and the former disease will be cured: fight like with like.