When we take the idea of immortality in the widest sense, and extend it to the totality of the knowable universe, it has a scientific significance; it is then not merely acceptable, but self-evident, to the monistic philosopher. In that sense the thesis of the indestructibility and eternal duration of all that exists is equivalent to our supreme law of nature, the _law of substance_ (see chap. xii). As we intend to discuss this immortality of the cosmos fully later on, in establishing the theory of the persistence of matter and force, we shall not dilate on it at present. We pass on immediately to the criticism of that belief in immortality which is the only sense usually attached to the word, the immortality of the individual soul. We shall first inquire into the extent and the origin of this mystic and dualistic notion, and point out, in particular, the wide acceptance of the contradictory thesis, our monistic, empirically established _thanatism_. I must distinguish two essentially different forms of thanatism--primary and secondary; primary thanatism is the original absence of the dogma of immortality (in the primitive uncivilized races); secondary thanatism is the later outcome of a rational knowledge of nature in the civilized intelligence. We still find it asserted in philosophic, and especially in theological, works that belief in the personal immortality of the human soul was originally shared by all men--or, at least, by all "rational" men. That is not the case. This dogma is not an original idea of the human mind, nor has it ever found universal acceptance. It has been absolutely proved by modern comparative ethnology that many uncivilized races of the earliest and most primitive stage had no notion either of immortality or of God. That is true, for instance, of the Veddahs of Ceylon, those primitive pygmies whom, on the authority of the able studies of the Sarasins, we consider to be a relic of the earliest inhabitants of India;[22] it is also the case in several of the earliest groups of the nearly related Dravidas, the Indian Seelongs, and some native Australian races. Similarly, several of the primitive branches of the American race, in the interior of Brazil, on the upper Amazon, etc., have no knowledge either of gods or immortality. This _primary_ absence of belief in immortality and deity is an extremely important fact; it is, obviously, easy to distinguish from the _secondary_ absence of such belief, which has come about in the highest civilized races as the result of laborious critico-philosophical study.