In publishing this paper I am fulfilling the wish of my beloved friend, Dorian Feigenbaum. It is a tragic coincidence that my last interchange of ideas with him was largely concerned with the problem of death and with mourning. In his last letters to me he pressed me repeatedly to send this paper, incomplete as it is, for the Quarterly. At that time we had no suspicion that this man, so full of the joy of life, so deeply and actively interested in everything intellectual, would himself become so soon an object of mourning to all those who knew and loved him.