Hippocrates (ca. 460-377 BC) postulated that "Disease is eliminated through means that can cause similar symptoms." Paracelsus (1493-1541) also claimed that "the same must be cured right away: false similibus curantur."
First, the German doctor and pharmacist Samuel Hahnemann (1755-1843) was put in a homeopathic system. Hahnemann experienced many of the contemporary medical treatments such as bled more harm than good. He spoke eight languages and used his language skills to translate the medicinal literature. The translation of Dr. William Cullen's A Treatise on Materia Medica led to the discovery of the homeopathic principle. The Dr. Cullen's drug handbook stated that quinine in addition to cure malaria fever also elicited malaria-like symptoms. Hahnemann had practiced in a swampy land area and had good experiences with quinine in malaria. He thought it was so strange that quinine could induce symptoms resembling malaria. He decided to test this, take some quinine.
To his astonishment, he developed fever symptoms. They disappeared as soon as he stopped taking quinine. After a break, he took quinine again, this time with some of his family members and colleagues. All developed the same symptoms. This strange phenomenon took Hahnemann strongly, that a remedy that was effective at a disease, at the same time elicited disease symptoms in healthy people. He began to wonder if he had stumbled upon the main principle behind all the medicinal effect. He did so, along with colleagues, painstaking effort over six years before he published his discovery of equality law. After a further 13 years, when he used drugs in their original form, he started based on his pharmacist training to experiment with different dosing methods. It was then that he discovered the special forerunning which he called potentiation.