In the Organon , Hahnemann states that each potency that is imposed onto an organism affects the vital force and creates an alteration in the patients´ state of being for some time (Aphorism 63). This is known as a primary reaction. The vital force though seeks to oppose this influence and induces a force encouraging rehabilitation to the initial healthy state of the patient (Aphorism 64). This is the curative action and is called the secondary reaction. It echoes Newtons´ third law that states that to every action there has to be an equal but opposite reaction . Cure should take place according to the law of Hering, which means from inside out, top to bottom and in reversed order of symptom appearance . Roy  describes primary and secondary reaction in more detail: The primary reaction of an appropriate homeopathic medication creates within the diseased individual a pseudo-ailment that mirrors in its expression that the patient is actually presenting with; pointed out also in the Organon in Aphorism 157 . This first reaction is an impulse to the vital force that triggers it to start opposing this alien disease agent. This oppositional stimulation, that seeks to resolve the diseased state, is the secondary reaction, the curative process that shall restore the patient to good health. This secondary action, the amelioration, should be widely symptom free.
Minor initial aggravations in the primary reaction, are considered a sign demonstrating that the remedy choice was indeed a closely matching one, but in highly sensitive patients there may be major homeopathic aggravations that suggest that the potency or the dosage had been inappropriately chosen . Secondary reaction aggravations occur if the selected remedy is only partially matching the case  or the dose is too high for the patient prone to susceptibility, this may lead to enduring ailments of this artificially induced disease . The appearance of new symptoms that stand in no relation to the presented ailment may be of the underlying condition surfacing as the prior layer has been removed, or symptoms of the remedy itself may be expressed . Little  (n.p.), calls this a “dissimilar aggravation” meaning that the patient has received a remedy that is not relevant for his cure. This may mean the patient is proving the remedy . Here an antidote should be administered prior to in-take of a more accurately matching prescription .
The remedy, if appropriately chosen should mirror the ailment the patient is presenting with. The action of the vital force to this stimulus, the secondary reaction, should be in opposition to the primary reaction, thus be able to remove the presented ailment once the artificial infection of the administered remedy has ceased . It is not always possible to find the exact matching remedy that will relieve the patient of all symptoms at once. This well chosen remedy may remove one layer of the patients presented state and may reveal another that will require a new remedy.
[Many thanks to Ian Townsend, University of Central Lancashire, U.K., for his assistance with this assignment]
 Hahnemann, S. (1974) Organon der Heilkunst (2.Auflage) 6B Heidelberg:Karl F. Haug Verlag.
 Close, S. (2000) The Genius of Homeopathy
Lectures and Essays on Homeopathic Philosophy Chapter 13 [online] last accessed 07.04.09 at URL http://homeoint.org/books4/close/chapter13.htm
 Koehler, G. (1989) The Handbook of Homeopathy Vermont, Healing arts press.
 Roy, M. (2006) Homeopathic case analysis Kilmarnock, Ritchie UK Ltd.
 Little, D. (2006) Hahnemann´s advanced methods [online] Homeopathic ezine, last accessed 06.04.09 at URL http://www.hpathy.com/philosophy/little-medicinal-solution.asp
 Sherr, J. (1994) The dynamics of proving Malvern, Dynamis Books