Samuel Hahnemann was a German physician who established a new system of medical treatment call homeopathy. He spoke many languages and supported himself as a translator while studying medicine, graduating in 1779.

Hahnemann became convinced that many medical treatments such as bloodletting did more harm than good, and looked for gentler ways to treat patients. He was one of many physicians in the 1700s who set out to explore systematically the use and effects of medical drugs.

Hahnemann suggested testing the effects of drugs on the healthy human body in order to obtain secure knowledge of a drug's effects. Following self-experimentation with the antimalarial drug quinine, Hahnemann noted that the drug had a similar effect to the illness it was supposed to cure - in a healthy person, a dose of quinine caused a fever. From this, Hahnemann developed the central idea of homeopathic medicine: the principle of 'like cures like' or the 'law of similars' - an idea that was also central to folk medicine.

When Edward Jenner introduced vaccination in 1798, Hahnemann considered this a confirmation of his principle. Hahnemann also came to assume that the body was highly sensitive to drugs during illness, and prescribed very small doses of drugs - hence the expression ‘homeopathic doses’ for very small amounts.

Homeopathy spread rapidly through Europe in the early 1800s. The first homeopathic hospital opened in 1832 in Leipzig. However, homeopathy also met with hostility from apothecaries and other medical practitioners. In 1835, Hahnemann moved to Paris, where he was a popular practitioner until his death.