Keeping an open mind - the theory

Homoeopathy was 'invented' by the German physician Samuel Hahnemann at the turn of the 19th century.  In about 1790 he was supplementing his income by translating medical texts into German.  While translating the 1789 Materia Medica by the eminent Scottish scientist William Cullen, he came across the statement that the bark of the cinchona tree is effective against malarial fever, including the author's assertion that the efficacy was due to the astringent action of the bark on the stomach.  Hahnemann was dubious about this claim, for the very good reason that many substances which have an even more astringent effect on the stomach have no discernible efficacy against malarial fever.

He acquired some of the bark, and self-administered it - although he was not himself suffering from malarial fever at the time.  He noted some very striking and apparently reproducible effects, including palpitations and trembling, which seemed to him to be similar in nature to the very fever the preparation was alleged to be effective in treating.  This observation is acknowledged to be the foundation of the entire 'science' of homoeopathy, and has been likened in importance to the occasion when Newton was struck by the falling apple.

The doctrine of 'like cures like'

Hahnemann's reasoning proceeded as follows:

  1. Cinchona bark produces fever-like symptoms in healthy individuals.
    False.  Although these symptoms were apparently reproducible in Hahnemann himself, many attempts to replicate the effect in other people have found nothing.  It has been suggested that Hahnemann in fact suffered from an allergy to some constituent of the bark, and that the effects he described were actually those of a mild hypersensitivity reaction (Thomas, 2002).
  2. The reason for the efficacy of cinchona bark in relieving malarial fever is that it produces the signs of fever in healthy individuals.
    False.  The reason for its efficacy is that it contains a high concentration of the alkaloid quinine, which is toxic to Plasmodium vivax.
  3. All effective drugs are efficacious because they produce the symptoms of the condition they affect.
    This hardly merits a reply.  Even in Hahnemann's time it was an enormous assumption which was not supported by observed fact, and the first person to protest that insulin will cause coma in non-diabetics will be taken out and shot.
  4. Effective drugs may be identified by investigating ('proving') the effects of a wide range of randomly-selected substances on healthy people.  A substance can be assumed to be an effective treatment for any condition characterised by clinical signs similar to those demonstrated by healthy volunteers when dosed with that substance.
    False in logic.  Even if points 1-3 were indisputably true, this would not necessarily imply the reverse, that any random substance can be assumed to be a useful drug simply on the basis of its observed effect on healthy people.

The subject of 'provings' is worthy of further consideration, particularly as it appears that it is this process referred to (rather than any objective assessment of efficacy) when it is asserted that homoeopathic remedies are 'well proven'.  Hahnemann's original record of the effects of cinchona bark are relatively clinical, but later investigations became very detailed, subjective accounts of every tiny sensation or emotion experienced by the subject, for several days or even a week or two after taking the supposed remedy.  These have been the butt of ridicule pretty much since they were published, nevertheless they are the foundation of homoeopathic practice.  Choice examples include:

Lists of symptoms associated with some substances run up to 50 pages, and even common food items are credited with wide-ranging effects - including 174 symptoms for green pepper.  However, many substances were 'proved' only once, with no attempt to ascertain whether the recorded effects were repeatable, either in the same or a different subject.  Where more than one individual was involved, observations were merely aggregated.

Most summaries of homoeopathic theory written for the non-expert assume, either explicitly or implicitly, that provings are done on appreciable amounts of substance.  A common tactic (used by Peter Fisher on the Horizon programme) is to invoke the obvious effects of raw onion on the eyes and nose, and explain that this is the rationale for using homoeopathic onion (allium cepa) as a treatment for colds or 'flu.  However, although Hahnemann's original investigations were indeed done in this way, after he had derived the 'doctrine of infinitesimals' (described below) he appears to have progressed to carrying out the provings on ultra-dilute preparations, until by 1833 he was recommending that these should all be performed using 30C 'potencies'.  Despite the fact that these preparations are completely solute-free, most homoeopaths (for example Hoare and Ebrahimi) appear to believe that they produce striking and undeniable effects on healthy individuals.  However, published reports of blind trials tell a different story (Walach, 1993; Goodyear et al., 1998; Vickers et al., 2001; Walach et al., 2001).

The art of homoeopathy involves matching the patient's complaint to the published provings, and thereby ascertaining the appropriate remedy.  Classically, therapy was individualised to the patient, and different remedies might be appropriate for the same presentation in different individuals.  The patient's 'constitutional type' was also a consideration, with certain personality types believed to have an affinity for particular remedies no matter what the presenting signs.  However, in modern times self-prescribing of off-the-shelf remedies has also become popular.

Classic homoeopathic proving simply cannot be carried out on an animal, and veterinary homoeopathy makes a virtue out of this difficulty.  One 'consultant' has boasted, "Every remedy has been meticulously proven, using volunteering people (never unsuspecting animals)...." (Mullan, 2001).  This certainly avoids problems with the animal rights lobby!  Choice of therapy is therefore by extrapolation from human homoeopathy, a good example being Mueller (2003), where the selection of the remedy appears to have been made more on the basis of the patient's 'constitutional type' than by matching the symptoms.  There is however nothing in the homoeopathic literature about the effect of Rhus toxicodendron (real or ultra-dilute) on a healthy Bearded Collie.

Hahnemann was so taken by his theory that he started to put it into practice, recommending some quite toxic therapies (such as strychnine, mercury and sulphuric acid) on the principle of 'like cures like'.  The effects were entirely as might be predicted, and it was obvious that the theory needed some refinement.

The doctrine of infinitesimals

In order to reduce or eliminate the toxic effects of his therapies, Hahnemann decided to reduce the dose - or rather, to administer more dilute preparations.  From there he progressed to very elaborate and repetitious serial dilution rituals, in which the original constituents were diluted out many thousand-fold.  Solvents used were water, alcohol or a water / alcohol mixture for liquid remedies, and powdered lactose for powdered substances.

His reasoning now proceeded as follows:

  1. Serial dilution removes the undesirable and toxic side-effects from the preparation.
  2. At the same time the desired therapeutic effect is not simply maintained in the solution, it is magnified - in fact the more dilution cycles involved, the more 'potent' the remedy.
  3. Impurities in the solvent, even if present in similar or greater concentrations to the remedy, have no effect.  The only property which is 'potentised' by the serial dilutions is the desired therapeutic effect of the designated remedy.

Although Hahnemann believed that matter was infinitely divisible, he appreciated that by the end of his dilution protocol there would be to all intents and purposes nothing left.  He therefore introduced the concept of a 'vital force' in the remedy, which was held to be released or potentised by the shaking procedure, or by grinding and pulverising the solid remedies.  It is likely that he derived this notion from the more occult regions of Freemasonry, in which he had been involved in the 1770s and 1780s (Ransom, 1999).  Although modern homoeopathic pharmacies generally use electrically-powered vortex mixers, Hahnemann himself was very specific about how many times the solution should be struck against a leather pad or leather-covered book.  (The story of "Oscillococcinum", a widely-used if perhaps rather non-standard remedy, is worth a closer look.)

This, then, is the theoretical basis of the 'science' of homoeopathy.  Modern observers may protest that it is unfair to criticise today's practitioners for the occultism of the founder, and that surely the practice nowadays is more rational.  However, although further doctrines have been accrued, such as the practice of giving mixed remedies and the prophylactic administration of 'nosodes' (sometimes termed homoeopathic vaccines) - both of which seem to contradict Hahnemann's original theories - modern homoeopathic medicine is in fact very little different from Hahnemann's time, and a description of his techniques gives a pretty fair impression of what is being done today.

It is true that many effective therapeutic techniques have been introduced by people who were either entirely ignorant of their mechanism of action, or entirely mistaken about it.  Cullen was just as wrong as Hahnemann regarding the mode of action of cinchona bark, but cinchona bark is nevertheless effective against malaria.  It is conceivable that all that testing of randomly-selected substances might indeed have turned up one or two therapeutically-active compounds by chance, though it has to be said there is no real evidence that this has occurred.  However, the general assertion that 'like cures like' has not only not been scientifically proven, the weight of evidence against it is now completely overwhelming.  Furthermore, the extreme dilution in which the remedies are administered (frequently 'ultramolar', that is so far beyond Avogadro's number that there is essentially no chance of even one molecule of the original remedy remaining) means that even the theoretical possibility of a chance therapeutic effect is no longer scientifically tenable.

So, what sort of science is homoeopathy ?

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GOODYEAR, K., LEWITH, G. & LOW, J. L. (1998)  Randomized double-blind placebo-controlled trial of homoeopathic 'proving' for Belladonna C30.  J. R. Soc. Med. 91(11), 579-82.

MUELLER, P. (2003)  Homoeopathy - what's in it?  Veterinary Review 77, 16-17.

MULLAN, G. (2001)  Turning to homeopathy.  Belfast News Letter, 25th August 2001.

RANSOM, S. (1999)  Homoeopathy - What are we Swallowing?  Uckfield, East Sussex: Credence Publications.

THOMAS, W. E. (2002)  Hahnemann's allergy to quinine.  Hahnemann's Homeopathy,

VICKERS, A. J., VAN HASELEN, R. & HEGER, M. (2001)  Can homeopathically prepared mercury cause symptoms in healthy volunteers?  A randomized, double-blind placebo-controlled trial.  J. Altern. Complement. Med. 7(2), 141-8.

WALACH, H. (1993)  Does a highly diluted homeopathic drug act as a placebo in healthy volunteers?  Experimental study of Belladonna 30C in a double blind crossover design - a pilot study.  J. Psychosomatic Res. 37(8), 851-860.

WALACH, H., KOSTER, H., HENNIG, T., & HAAG, G. (2001)  The effects of homeopathic belladonna 30CH in healthy volunteers - a randomized, double-blind experiment.  J. Psychosomatic Res. 50(3), 155-160.