It has been said a thousand times and in a thousand books that ancestor-worship is for the most part the source of primitive religions, and it may be strictly said that what most distinguishes man from the other animals is that, in one form or another, he guards his dead and does not give them over to the neglect of teeming mother earth; he is an animal that guards its dead.

The Tragic Sense of Life (1913) - III : The Hunger of Immortality