Although the biological system is a combination of different chemical processes,many of the mechanisms can not be explained by general chemical processes.Therefore,as a driving force of biological system,a distinct entity called'vital force'can be imagined.But this is not essential to explain homeopathy.From the analysis of different phenomena it apparent that biological system has a tendency to maintain a balanced state.Such a good example is catch-up growth.A stimulus is required to disrupt the balance.This stimulus must enter the body from outside or in case of disease it must arise from within inside.This is the primary stimulus.Infection,chronic poisoning,etc.help the expression of the internal stimulus.These are secondary stimulus.The active dose of similar drug acts on the terminal site of the disease process.This causes the actual reversal of the disease process.Allopathic dissimilar drugs act on different stages of the disease process and alter the course of the disease process.The effect of allopathic drugs does not destroy the effect of disease and compete with the effect of the disease.Potentized homeopathic remedies neutralize the effect of disease but do not alter the course of the disease.As a result,either symptoms of the disease are neutralized or the disease process is accelerated.Different other phenomena support that the property of the potentized remedy is not similar to the original substance.It is a new property which is negative pharmacological property.