Dr Samuel Hahnemann (1755-1843) observed that there were general tendencies in the way that his patients got ill and then well again,  but it was Dr Constantine Hering (1800-1880) who codified this pattern, based on the growing quantity of observations by homeopaths. He was originally commissioned to expose homeopathy as false, and decided that in order to attack it more successfully, he needed to study it carefully. As a result he became one of the great homeopaths and formulated the homeopathic ‘law of cure’:
First, he observed that the human body seeks to externalize disease – to dislodge it from more serious internal levels to more superficial external levels. …
Hering’s second observation was that healing progresses from the top of the body to the bottom. …
Hering’s third observation was that healing proceeds in the reverse order of the appearance of symptoms.
Thus, the most recent symptoms will generally be the first to be healed. For this reason, in the process of cure a person may sometimes re-experience symptoms he or she previously suffered from (generally those symptoms that were suppressed or never really healed). 
Just as any scientific law can be used to assess the result of an experiment, Hering’s ‘law of cure’ allows the result of any medical treatment to be assessed, whether homeopathic or otherwise. This is because it enables practitioners to relate patients’ complex individual reactions to general principles.
1. See Samuel Hahnemann (trans. William Boericke), The Organon of Medicine, 6th edn, manuscript completed in 1841 (Calcuta: Roy Publishing House, repr. edn 1972), §§ 201-204 and 214-220, pp. 225-228 and 234-237.
2. Dana Ullman, Discovering Homeopathy: Your introduction to the science and art of homeopathic medicine, revised edn (Berkeley: North Atlantic Books, 1991), p. 17.
Why it works