Homeopathy is a method of treating the sick developed by Samuel Hahnemann, M.D. (1755–1843), an eminent German physician and professor of pharmacology. It is practiced by licensed physicians and other health professionals throughout the world. Homeopathic remedies are protected by federal law, and are obtainable without prescription for first–aid and domestic use.

In a series of experiments from 1792 onwards, Hahnemann demonstrated:

• That medicinal substances regularly produce in healthy people the same symptoms that they cure in the sick; and,
• That the medicine–producing symptoms most similar to the illness as a whole is most likely to initiate a genuinely curative response (i.e., one that completes itself spontaneously without further assistance).

Hahnemann understood these experiments to mean that the manifest symptoms of illness already represent the attempt of the organism to heal itself, and the similar remedy acts by reinforcing that effort in some way.

Hahnemann also showed that true cure necessarily involves a concerted response of the whole organism, since the similar remedy acts only if it is correctly chosen, if its detailed similarity to the illness somehow renders the patient abnormally sensitive to it. Otherwise, the minuteness of the dose makes it likely that little or nothing will happen—a crucial safety feature.