Hahnemann's principle work, ‘The Organon of Medicine’ (published in 1810) contains the principles of the therapy he called homeopathy.

Hahnemann rediscovered the Law of Similars, whereby the sum of the symptoms is treated according to the principle of similarity (like cures like).

The appropriate homeopathic medicinal product, know as the Similimum, is often a much reduced dose of the substance which in larger quantities would create similar symptoms in a healthy person. It stimulates the body’s defence against such symptoms and it mobilises the organism's self-healing capacity.

The Law of Similars goes back to antiquity. Hippocrates first referred to it in his various writings. He mentioned that a substance that causes painful urination, coughing and vomiting would also cure diseases with these symptoms. In one of his books he mentions that turpentine will both produce and check haemorrhages in women depending on the quantity used.

So for example, allium cepa (onion) is a homeopathic remedy commonly used for treating the symptoms of hay fever (running eyes).

The test with a substance on a healthy person is called a ‘proving’. In 1796 after many provings the Law of Similars – Similia Similibus Curentur (Let like be cured by like) - was formulated in his essay: ‘Essay on a New Principle Whereby the Healing Properties of Medicinal Substances are Revealed, in Addition to a Few References at Preceding Ones’.

Hahnemann’s approach was holistic. He believed that disease is an individual process which develops differently in each human being and thus requiring an individually adapted treatment. All symptoms of a disease - physical, mental and emotional - contribute to the entire picture. The best results are obtained when a good match is struck between the remedy picture and the individual’s symptoms, regardless of the actual disease.