This book is a sequel to my treatise called The Shudras-Who they were and How they came to be the Fourth Varna of the Indo-Aryan Society which was published in 1946. Besides the Shudras, the Hindu Civilisation has produced three social classes whose existence has not received the attention it deserves. The three classes are :-(i) The Criminal Tribes who number about 20 millions or so;(ii) The Aboriginal Tribes who number about 15 millions; and(iii) The Untouchables who number about 50 millions.The existence of these classes is an abomination. The Hindu Civilisation, gauged in the light of these social products, could hardly be called civilisation. It is a diabolical contrivance to suppress and enslave humanity. Its proper name would be infamy. What else can be said of a civilisation which has produced a mass of people who are taught to accept crime as an approved means of earning their livelihood, another mass of people who are left to live in full bloom of their primitive barbarism in the midst of civilisation and a third mass of people who are treated as an entity beyond human intercourse and whose mere touch is enough to cause pollution?In any other country the existence of these classes would have led to searching of the heart and to investigation of their origin. But neither of these has occurred to the mind of the Hindu. The reason is simple. The Hindu does not regard the existence of these classes as a matter of apology or shame and feels no responsibility either to atone for it or to inquire into its origin and growth. On the other hand, every Hindu is taught to believe that his civilisation is not only the most ancient but that it is also in many respects altogether unique. No Hindu ever feels tired of repeating these claims. That the Hindu Civilisation is the most ancient, one can understand and even allow. But it is not quite so easy to understand on what grounds they rely for claiming that the Hindu Civilisation is a unique one. The Hindus may not like it, but so far as it strikes non-Hindus, such a claim can rest only on one ground. It is the existence of these classes for which the Hindu Civilisation is responsible. That the existence of such classes is a unique phenomenon, no Hindu need repeat, for nobody can deny the fact. One only wishes that the Hindu realised that it was a matter for which there was more cause for shame than pride