This section is from the book "A Compend Of The Principles Of Homoeopathy", by William Boericke. Also available from Amazon: A Compend of the Principles of Homoeopathy as Taught by Hahnemann.
The indicated remedy in any case is the remedy that corresponds to the totality of symptoms, as interpreted according to the relative rank of symptoms, and not one covering, merely some isolated characteristic or key-note symptom, or, on the other hand, one that corresponds merely to the pathological lesion. The objections to the key-note system of selecting the remedy are its disregard for the fall study of the remedy and elevation, instead of some minor often clinical symptom, yielding at best only palliative results, while the objection to the pathological basis is its incompleteness, being only a partial picture of the totality of symptoms and therefore an unreliable basis for curative prescribing.
The similimum is the most similar remedy corresponding to a case, one covering the true totality of symptoms, and when found, is always curative, and in incurable cases, it is the best possible palliative remedy.
Unfortunately, in the present state of our Materia Medica, and other limitations of our art, the Similimum in any case of illness, is not always discoverable. Nevertheless, a cure is possible, albeit, not so prompt as it would be if the chosen remedy were the Similimum to the case. While this is the ideal to be sought, the prescriber must more frequently be satisfied with the selection of a mere similar instead. Fortunately, the very conception of similarity is one of relative nearness and does not express an absolute relation; it is comparative always, thus a drug is more or less similar according to the nearness of its correspondence to the totality of symptoms. Moreover, the experience and practice of the homoeopathic school teaches that anyone of several more or less similar remedies may be used with alike good results, that is, it may be sufficiently similar to bring about nature's reaction.
The merely similar remedy, though falling short of the dignity of the Similimum is not thereby removed from capacity of curative service, but the curative response is not as direct and prompt as results from the administration of the similimum which must ever be, in every homoeopathic prescription, the ideal to be sought.
The selection of the Similimum involves its administration singly and without admixture of any other medicinal substance.
The single remedy is the necessary corollary to the similar remedy. It is to be given alone, not alternated or mixed with any other *. Only then can its pure effects be evolved and estimated, and the single remedy must be given in the smallest dose that will bring about nature's reaction. The single remedy does not mean a simple remedy. All chemical salts, which are composite substances, the juice of plants, like Opium, a most marvelously compounded substance, are all single remedies and used as such in homoeopathy. Any single substance that has been proved upon the healthy, as an entity and whose pathogenesis is known, can be administered; but it must be given unmixed with any other medicinal substance, so as to obtain its own peculiar drug force unmodified by any other.
It is the similar relationship alone that constitutes the homoeopathicity. The size of the dose has comparatively little to do with it, except so far as experience may indicate it. It may be given in a crude form, wholly unprepared by the pharmacist's skill, or in material dosage, provided it does not produce temporary aggravation of the symptoms; or it may be administered stripped of all its apparent material, visible and tangible particles. Experience alone can teach which will bring about the best results in any given case.
* As early as 1797, Hahnemann wrote, in Hufeland's Journal, that for several years he had never administered anything but the single remedy at a time, and never repeated the dose until the action of the first had expired.
Alternation or rotation of remedies is reprehensible practice, since it leads away from accurate and definite knowledge of drug effects, and sooner or later leads to polypharmacy, which is the most slovenly of all practice. Since we have no provings of combination of drugs, it would be impossible to prescribe such combinations with scientific accuracy. In regard to alternation, Hahnemann says: "Some homoeopathists have made the experiment in cases where they deemed one remedy suitable for one portion of symptoms of a case of disease, and a second for another portion, of administering both remedies at once, or almost at once; but I earnestly deprecate such hazardous experiments, that can never be necessary, though they sometimes seem to be of use". Note to § 272, Organon.
For further study, read -
Dunham: "Science of Therapeutics - Alternation of Remedies".
Edmund Capper: "The Method of Hahnemann and the Homoeopathy of To-day," in Journal of British Homoeopathic Society, January, 1895.
Jones: "The Ground's of a Homoeopath's Faith". Lecture 2: "The Single Remedy".
Joslin: "The Principles of Homoeopathy - The Single Remedy".
Eleanor F. Martin, M.D.: "The Single Remedy vs. Alternation," in Pacific Coast Journal of Homoeopathy, October, 1894.