M. Yves Delage[101] in an analysis of my “Nature of Man” doubted the existence of an instinct for death. “Animals,” said he, “cannot have the instinct for death, because they do not know of death. In their case, we must consider that what happens is an apathy tending to the abolition of the sense of self-preservation. In man, the knowledge of death implies that the indifference to its approach cannot be an instinct.” “There may be developed, at the end of life, a special state of mind which accepts death with indifference or with pleasure, but such a state cannot be designated as an instinct.” M. Delage, however, does not suggest what the state of mind in question is to be called. As the aunt of Brillat-Savarin compared her sensations just before death with the desire to sleep, and as this desire is an instinctive manifestation, I think that the cheerful acquiescence in death, exhibited by extremely old people, is also a kind of instinct. However, the important matter is that the sentiment exists, and not what we are to call it. M. Delage is far from denying its existence. Dr. Cancalon,[102] another of my critics, cannot admit the existence of an instinct of death, “because of the theory of evolution. Of what good would it have been, as M. Metchnikoff tells us that natural death is very rare; how could it have been transmitted, as it comes into existence long after the age of reproduction, and how could it have aided the survival of the species? If its existence were proved as the result of biological evolution, it would be a contradiction of adaptation and an argument in favour of final causes.” I cannot agree in any way with these opinions. In the first place, it is well known that men and animals have many harmful instincts that do not tend to the survival of the species. I need recall only the disharmonic instincts which I described in the “Nature of Man,” such as the anomalies of the sexual instinct, the instinct which drives parents to devour their young or which attracts insects to flames. The instinct of natural death is far from being harmful, and may even have many advantages. If men were convinced that the end of life were natural death accompanied by a special instinct like that of the need for sleep, one of the greatest sources of pessimism would disappear. Now pessimism is the cause of the voluntary death of a certain number of people and of many others refraining from reproduction. The instinct of natural death would contribute to the maintenance of the life of the individual and of the species. On the other hand, there is no difficulty in admitting the existence of instincts hostile to the preservation of the species, especially in the case of man, in whom individualism has reached its highest development. As man is the only animal with a definite notion of death, there is nothing extraordinary if it is in man that the instinctive wish for death develops. M. Cancalon denies the possibility that death can be pleasant, as it is