Siddha generally refers to Athma Siddha that is the 8th supernatural power. Those who attained or achieved the above said powers are known as Siddhars. There were 18 important siddhars in olden days and they developed this system of medicine. Hence, it is called Siddha Medicine. Basic Principles Siddha science considers nature and man as essentially one.
Nature is man and man is nature.
Man is said to be the microcosm and Universe is the macrocosm because what exists in the world exists in man. Man is nothing but a miniature world containing the five elements of the various principles which constitute the minerals, vegetables and the animal kingdom. According to Siddha medical science, the Universe originally consisted of atoms which contributed to the five basic elements, viz., earth, water, fire, air and sky which correspond to the five senses of the human body and they were the fundamentals of all the corporeal things in the world. A close relationship is found to exist between the external world and the internal system of man. Man consumes water and food, breathes the air and thus maintains the heat in the body.