The principles which govern the selection and administration of homoeopathic remedies are very simple.
The great law, Similia Similibus Curentur, teaches us to select a remedy the characteristic pathogenetic symptoms of which are very similar to those of the patient. This is a grand generalization, supported by a multitude of facts. We accept it. It takes no heed of names of diseases, nor of pathological theories of the seat and origin of diseases. Giving a broad and liberal signification to the word “symptom” so as to include everything abnormal about the patient, whether it be historical or actual, this law pays regard to the symptoms alone. It requires that the symptoms shall be collected and compared with the Materia Medica every time a prescription is made, and that the drug that has produced symptoms most similar to those of the patient shall be chosen and given. This is a true homoeopathic prescription. No matter how often during the sickness of a patient this process be repeated; no matter how many remedies be given in succession; no matter if the first remedy be recurred to after the second and the second after the first – if each prescription have been the fruit of a special collection of symptoms and comparison of them with the Materia Medica – call it “alternation,” or by whatever other wrong name you please, it is a sound and defensible homoeopathic prescription, such as Hahnemann taught and practised and his followers adopted.
Reference: Caroll Dunhmam