The term Posology originates from Greek words 'posos' meaning 'how much' and 'logos' meaning 'study'. In homeopathy, Posology means the doctrine of dose of medicine. A homeopathic dose means the potency, quantity and form of medicine as well as repetition. As it is a very lengthy topic to explore, I will just focus on the potency selection part of Posology.

Before we try to learn more about the potency selection, let us first summarize what potencies are available to a homeopath.
1. The Centecimal Scale, evolved by Hahnemann, denoted by the numerical designation of the potency or by the number followed by the suffix C or CH, e.g., 30C or 200C.
2. The Decimal Scale, evolved by Hering and denoted by the suffix X, after the number, e.g., 200x.
3. The 50 Millesimal or LM Scale - also known as Quinquagintamillesimal or Q potencies. Hahnemann evolved this scale in the last years of his life.

Potencies can be broadly classified as low, medium, and high. Low potency designates anything from Q to 12C, medium from 12C up to 200C and high from 200C upwards to DM, MM, DMM.

It is believed that the higher potencies were first prepared by Korsakoff in 1834 but came in popular use with Jenichen's high potencies after 1844.

Now coming back to the question of potency selection, we will start exploring the views of renowned homeopaths of various eras. It would be appropriate to begin our tour with Hahnemann himself - the person who conceived homeopathic potencies.

Hahnemann first started to employ 'similar' medicines around 1790 and 8 years later began to experiment with gradual reductions in dosage. As a physician, he clearly became increasingly satisfied with the results of using dynamized medicines, because he continued to use them in preference to material doses until the end of his long life.

He started to conduct the very first experiments with dose reduction in the year 1798. This includes 2x, 4x and 2c. According to Peter Morrel's research, In 1799 Hahnemann began to reduce the dose further, using 5x, 6x, 3c and 8x. In 1800 he begins to use 10x and in 1803 12c appears for the very first time. In 1805 the 18th centesimal dilution appears, which was to prove one of the most consistently favourite potencies that he used throughout his long career. In 1816 30c makes its first appearance and this remained his most extensively used and most highly recommended potency of all time.

Further developments include the first mention of 6c in 1819 and the first mention of 60c in 1824. In 1830 he first mentions Olfaction as a means of drug administration and this remained a very popular method with him until the end of his life. Finally, in 1838 the LM potencies make their first appearance. Towards the end of his life, he was moving more and more towards the use of LM potencies but still gave Centesimal potencies to majority of his patients.
During Hahnemann's lifetime, he is known to have generally used only potencies up to 30C. But Farrington quotes Madame Hahnemann as saying that he had used the 200th and the 1000th when necessary. The 1000th, however, he seems to have used only once.

Beyond Hahnemann

Even during the life of Hahnemann there was a split among homeopaths. A section believed in the use of potentized remedies and another believed in crude doses on the basis of Simila. Among those who used the potentized remedies, most were not in favor of very high potencies. During the later years of Hahnemann, the proponents of the crude doses decreased and the higher potencies came into greater use.

Homeopaths of all times have remained divided over the question of potency selection and even 160 years after Hahnemann's death, the question of potency selection is still open-ended. Let us take a look at the views of some leading homeopaths of different eras.

Boenninghausen, a contemporary of Hahnemann, was clearly in favor of high potencies. He wrote many papers in support of high potencies and listed therein many advantages like -
1. The sphere of action continually enlarges with high potencies so that in chronic ailments they hasten the cure,
2. In acute diseases, the effect appears quicker, and
3. They act in spite of discretion in diet.

Homeopaths like T. F. Allen, Richard Hughes, Dr. Wilson, Dr. Henry Dearborn, J. H. Clarke, Dr. George Royal, Boericke, Pierce, Edgar were in favor of low potencies and advised the same in most cases. On the other hand homeopaths like Boenninghausen, Hering, Lippe, Guernsey, Raue, Dunham, H. C. Allen, Kent, Boger, Nash, Roberts were all in favor of medium and high potencies. We can add to this list the names of Bell, Beronville, Borland, Stuart Close, Curie, Dewey, Gross, Fincke, Swan, Skinner, Jenichen, Ghose, Grauvogl, Hubbard, Sir John Weir, Margaret Tyler, Pulford, Templeton, Yingling, Waffensmith, P.P. Wells and Pierre Schmidt etc. All these homeopaths used the higher potencies with great success.

Most modern homeopaths like George Vithoulkas, Rajan Sankran, Jan Scholten, Prafull Vijayakar, Bill Gray, Robin Murphy, Alfons Geukens, Vesalis Ghegas, Massimo Mangilavori, Banerjeea, Anne Schadde, Luc de Schepper, Andre Saine, Eileen Naumann, Jayesh Shah, Jermey Sherr, Tinus Smits, Wolfgang Springer, Alize Timmerman etc. seem to be in favor of using higher potencies. Being in favor of high potencies does not mean using the high potencies to the exclusion of lower ones. The master homeopaths of the past and the present have been able to use the full range of potencies, from lowest to the highest, depending upon the case. The potencies most commonly used now a days are 6C, 30C, 200C, 1M, 10M, CM and the LM scale.

The LM scale has not been very popular among homeopaths, primarily due to historical reasons. It now seems to be coming into greater use as modern homeopaths are experimenting with it more and more. The likes of Schmidt, Kunzli, Voegeli, Patel, Chaudhary and Sankaran etc. have reported many cures with the use of LM potencies.

Now let us go through the views of some of these homeopaths in detail.

Boger seems to have utilized all potencies but was partial towards very high potencies. His favorite prescription appears to have been a single dose of DMM.

Borland says that in treating purely local conditions, remedies for the organ or tissues may be used in low potencies, as also in advanced pathological conditions and sensitive patients. When there is general similarity in addition to local indications, medium or high potencies may be preferred. He also says the more acute the disease, the higher the potency.

Clarke says that for ordinary practice, with acute illness, the lower dilutions from the 1C to 3C will be most useful. For chronic diseases, the higher dilutions would be required.

Close gives the following considerations that influence the choice of the dose -
1. The greater the characteristic symptoms of the drug in the case, the greater the susceptibility to the remedy and the higher the potency required.
2. Age: medium and higher potencies for children
3. Higher potencies for sensitive, intelligent persons.
4. Higher potencies for persons of intellectual or sedentary occupation and those exposed to excitement or to the continual influence of drugs.
5. In terminal conditions even the crude drugs may be required
He also writes "Different potencies act differently in different cases and individuals at different times under different conditions. All may be needed. No one potency, high or low, will meet the requirement of all cases at all times."
Curie opines that in acute diseases the low dilutions are to be preferred but in chronic diseases, the high dilutions promise greater success.

Edgar reports having treated cases successfully for twenty-five years with low dilutions and mother tinctures.

Gentry feels that in progressive diseases such as fevers and contagions, remedies must be given in medium or low potencies.

Blackie reports that in cases of real organic change due to infective causes a high potency might clear them up.

Grauvogl enumerates some rules for the use of potencies. He writes -
1. If we have to act on single parts, against single qualitative cause, we had better use low dilutions, as in haemorrahge before or after childbirth.
2. With high potencies, symptoms pass away quietly leaving no trace.
3. In dealing with a change of process of reduction or of oxidation or vice-versa, we must use the low dilutions.
4. But to dissolve process of retention, high potencies are indicated.
5. Nutritive remedies act better in low dilutions, functional remedies in high dilutions.
6. A chronic case, esp., when based upon retention in a carbo-nitrogenoid constitution, can be cured best by high potencies.

"After 30 years of careful observation and comparison with the use of various potencies, it is possible to lay down the following rules: Every physician should have at command the 30th, 200th, 1M, 10M, 50M, CM, DM, and MM potencies...From the 30th to the 10M will be found those curative powers most useful in very sensitive woman and children. From the 10M to the MM all are useful for ordinary chronic diseases in persons not so sensitive. In acute diseases, the 1M and 10M are most useful. In the sensitive woman and children, it is well to give the 30th and 200th at first, permitting the patient to improve in a general way, after which the 1M (and 10M) may be used in a similar manner. In persons suffering from chronic sickness and not so sensitive, the 10M may first be used, and continued without change so long as improvement lasts; then the 50M will act precisely in the same manner."

He further writes: "When the similimum is found, the remedy will act curatively in a series of potencies. If the remedy is only partially similar, it will act in one or two potencies and then the symptoms will change and a new remedy will be required."

Nash was also strongly in favor of medium and high potencies.

Pulford writes: "Lower potencies simply allay the predisposition (palliation or suppression) …The low curative remedies range from 30X to CC (200th) potencies, especially for acute cases which do not rely on, nor are part of a deep chronic malady. The medium curative remedies range from CC to 10M potencies in subacute cases all of which rest upon some deeper dyscrasia. The higher potencies range from the 10M up for the chronic curable cases."

Roberts advises that if the symptoms are very similar, we can go as high as we wish. The less sure we are of our similarity, the lower our potencies. As a rule when there is pathology, medium or high potencies may be dangerous.

Sir John Weir, quoting from his 35 years of experience says that low potencies should be used for physical illness, external conditions, skin conditions etc. When mental symptoms are found, high potencies are needed.

Constantine Hering says: "If the symptoms of the case generally have more resemblance to the primary symptoms of the drug then lower potencies, on the contrary more resemblance with the later effects (secondary action) thence advocate higher potencies."

Fergie Woods states that with sensitive patients, high potencies may aggravate. In cases with organic changes, lower potency is preferred. Particularly in cases of Phos. and Lach., he generally started with 12th only. He also mentions his opinion that the high potencies seem to act for a longer period merely because we give high potencies when we are more sure of the similimum.

Yingling, that remarkable homoeopathic obstetrician, writes, "There is no question but that the crude or very low potency will cure when homoeopathic to the diseases condition. Experience teaches and proves this beyond a doubt. But the experience as fully and completely proves and establishes the fact that the high and higher potencies act more promptly and efficiently and will cure cases, especially of chronic diseases, that the crude cannot touch. It is erroneous to suppose that the high potencies excel in the treatment of chronic cases and are not efficient in the acute stages of disease. My experience goes to prove that the high potencies are more reliable and efficient in the acute cases and will abort sickness or restrict it to a few days, whereas the crude would require many days or weeks to accomplish the same."

Hubbard says for the diseases of psychic origin the high potencies should be employed. Functional diseases too with subjective symptoms respond well to high potencies. Acute disease, even with pathological changes, will also need high potencies, while in acute crisis of chronic diseases such as cardiac asthma, medium or low potencies would be preferable. In chronic cases, it is safe to begin with 200C. She prefers high potencies in cases with marked mental symptoms. She also writes "In desperately ill cases, where the fight for life is active, in acute diseases, the high potencies are indicated; also, where the desperate illness is in the terminal stage of chronic disease the very high potencies induce euthanasia. In chronically incurable cases, unless the vitality is very good and pathology not yet too extreme, low or medium potencies are suitable"

She further writes: "The degree of susceptibility of your patient also influences potency selection. Certain persons are oversensitive (often owing to improper homoeopathic treatment) and they will prove any remedy you give them; they require, therefore, medium or low potencies. Other patients are very sluggish (often owing to much allopathic drugging). These will often take a very high potency to get any action at all or they may need a low potency repeated every few hours until favorable reaction sets in. A third type of patient is the feeble one where the vital force can easily be overwhelmed. Repetition is the greatest danger here. Acutely sick, robust patients will stand repetition of high potencies until favorable reaction commences, although the ideal is the single dose. Children take high potencies particularly well, and in general the very aged require medium potencies except for euthanasia. Some individuals have idiosyncrasies even to homoeopathic potencies of certain substance. Some degree of idiosyncrasy to a remedy must be present or the patient will not be sensitive enough to be cured, but where this is extreme the low or medium potencies should be preferred. Where patients are habitually poisoned by a crude substance, as a general rule it is not advisable to give that substance in very high potency, it is better to give an antidotal substance high."

P. Sankaran has laid some tentative rules for potency selection -

1. When in a case, the symptoms of the patient are very well matched by the symptom picture of the drug and especially if the mental symptoms are present and clearly marked, then a high potency seems advisable.
2. (a) Where the symptom matching is poor due to paucity of symptoms or (b) when the prescription covers only a superficial or local condition e.g. a skin condition such as a wart or (c) where pathological symptoms predominate, e.g. as in cancer, congestive cardiac failure, etc. or (d) where only a palliation is aimed at because the patient is incurable and has a very low vitality, low potencies seem more advisable.
3. Certain medicines seem to act better in particular potencies. For instance, drugs like Apocynum cannabinum, Sabal serrulata, Ornithogallum umbellatum, Hydrocotyle asiatica, Passiflora incarnata, Crataegus oxycantha, Adonis vernalis, Strophanthus hispidias, Carduus marianus, Blatta orientalis, etc., seem to act better in O.
4. Nosodes seem to act better in high potencies, e.g. 200 and above.
5. As regards bowel nosodes, certain rules apply. If the case is a new one and the patient has not received any potencies so far, a medium or high potency can be given when the bowel nosode is clearly indicated. If the patient has received any potency within the preceding 3 months it is wise to give a low potency. John Paterson writes that where there is marked pathological evidence, low potencies (below 6C) can be given and repeated daily. In acute diseases, the single high dose is preferable. For acute phase of chronic disease, high potencies can be given and repeated at intervals.
6. If the patient has already received a deep-acting constitutional drug in high potency and is improving under the action of this, but has developed some superficial disturbing symptom, a low potency of a complementary drug may be prescribed for the relief of the symptoms.
7. Children appear to tolerate high potencies well due to their vitality while old persons may not tolerate high potencies so well.
8. When the patient is oversensitive to drugs, it is wise to use a low potency.
9. When the reaction is poor and a reaction remedy is prescribed to promote reaction, e.g. Carbo veg., a high potency is to be preferred.
10. Probably intelligent and sensitive patients and those engaged in mental occupations need higher potencies while the dull and the backward and those engaged in physical work may need the lower ones. Extending this idea, it seems that the less highly evolved animals may need lower potencies.
11. Certain potencies may produce certain effects, e.g. it is said that Silica given in low potency promotes suppuration, whereas if given in high potencies it aborts suppuration.
12. High potencies of deep-acting medicines such as Silica, Phos., etc., are contraindicated in advanced pathological states.

Among the contemporary homeopaths, George Vithoulkas lays the following guidelines in his work "The Science of Homeopathy" -

"Patients who have weak constitutions, old people, or very hypersensitive people should initially be given potencies ranging, roughly, from 12 X to 200. The reason for this is that higher potencies can over stimulate the weakened defense mechanism, resulting in unnecessary powerful aggravations. The principle particularly applies to patients known to have specific pathology on the physical level.

Oversensitive patients …are very reactive to both low potencies and high potencies. Consequently it is better to restrict initial prescription to 30 or 200 in such patients.

Children who are suffering from severe problems should generally be given low potencies. …Cases with known malignancy should not be given potencies above 200.

If a case seems relatively curable and free of physical pathology, higher initial potencies may be tried, ranging from 30 to CM. The primary guiding principle here is the degree of certainty, which the homeopath has about the remedy.

Medicines such as Lachesis, Aurum, and Nosodes have strong tendency toward physical pathology. For this reason, they should usually be restricted to lower potencies (30 or 200) unless the individual case is demonstrated to be quite free of physical pathology.

In children with acute ailments, it is best not to give potencies lower than 200 …If the patient is elderly, chronically weakened, or even if severely weakened by the acute ailment, a 200 potency would be preferable for the initial prescription."

Rajan Sankaran writes: "The selection of the potency depends, … on the intensity, clarity and spontaneity of the symptoms expressed - especially of the peculiar symptoms, which reflect the individuality of the person. Consider the following:

A patient comes and says, " I don't know why but I often feel that I am poor, that I look like a beggar and am wearing tattered clothes."
Here we have an intense, clear and spontaneous expression. In such a case, I would almost invariably give a high potency (perhaps 10M); all other considerations, such as pathology, etc., would be secondary.

Of course, the potency also depends on the nearness (similarity) of the remedy to the case. The patient may be clear about his symptoms, express it with intensity and spontaneity, but the remedy selected may not have that feeling as intensely or clearly. In such a case the potency will depend on the extent to which the drug selected expresses the feelings of the patient."
Rajan Sankaran is also known to use LM potencies when the patient is very oversensitive.

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So we see that in spite of differences in the guidelines for potency selection, most modern homeopaths have some agreement on the factors which influence the selection of potency. These include -
1. Certainty about the remedy chosen
2. Kingdom of the medicine (source)
3. Age of the patient
4. Gender of the patient
5. Occupation of the patient
6. Sensitivity of the patient
7. Vitality of the patient
8. Nature of the patient
9. Type of disorder - Functional or Pathological.
10. Severity of Pathology
11. Acute or Chronic nature of the disease
12. Clarity and abundance of mental symptoms
13. Type of response desired - palliation or cure
14. Level of proving
15. Nature of drug
16. Miasm of the patient

The guidelines given by Hubbard, P. Sankaran, Vithoulkas and Rajan more or less summarize the clinical approach that one should have for potency selection. The only problem that we see these days is that a large majority of homeopaths practice with very limited range of potencies. There seems to be some hesitation in using very low potencies like mother tinctures and 1x, 2x etc. and at the same time most people are also not ready to try very high potencies like CM, MM, DMM. Due to this reason often a correctly chosen remedy does not give the desired result and instead of changing the potency, the homeopath often changes the remedy.

A homeopath should be open to using the full range of potencies available to him. The certainty in potency selection grows with experience. If you are confident of your remedy selection and the desired action is not there, try changing the potency to higher or lower before you decide to change the medicine itself. You cannot be flexible in your remedy selection; for cure, a remedy has to be similar, but you can be flexible about potency selection. A given case may respond to more than one potency of the same medicine. While choosing the potency just remember Hahnemann's words that an ideal cure has to be quick, gentle and permanent. Things will become easier from thereon!