This is the core concept of homeopathy. The therapeutic law on which Homeopathy is based is "Similia Similibus Curentar" which means 'let likes be cured by likes". In this art of healing the medicine administered to a diseased individual is such that if given to a healthy person it will produce similar sufferings as found in the diseased individual.
Thus the symptoms of the diseased individual have to be matched with the pathogenesis of the medicine and the medicine which is the most similar (Similimum) is selected and administered with certainty to cure.
According to homeopathy one single remedy is given to the patient at a time. The medication and the dosage will depend on each patient's constitution.
Every medicinal substance has characters of its own (i.e. pathogenitic effects) which differentiates it from all the other medicines.Thus medicines are proved on healthy human beings singly and in simple form without admixture of any other substances.
Similarly they are prescribed singly as effects of combination of medicines are not known and its action is confused .Surrogation in proving or prescription is thus impossible.
The smallest possible dose of homoeopathic medicine, just strong enough to create the stimulation of the system is considered adequate.
The minutest quantity of medicine helps it to reach the disease which of very subtle nature. As the action is at the dynamic level the minimum dynamic dose of the remedy is necessary.
As homeopathic medicines are human specific and that is the reason why it is so effective in treating the sick individual who also expresses his symptoms individuality.
Cure takes place from above downward, from within outward, from a more important organ to a less important organ; symptoms disappear in the reverse order of their appearance, the first to appear being the last to disappear.
For e.g. if you have walked a particular way in a room you will follow the same way to go out.
Suppose you have suffered from cold followed by asthma .The when cure takes place the asthma will get alright first then the cold will reoccur and finally the cold get better and the patient cured.
Another e.g. if patient suffered from skin problem which was suppressed and the patient develops insomnia when treated homeopathic medicines first the insomnia will get alright and then the skin eruptions will come back and finally everything will settle down that is cure as it is termed.