The sole fact of experience that demonstrates that life is generally good is that the overwhelming majority of men prefer it to death. For this to be so it must be that in the average existence happiness triumphs over unhappiness. If the relationship were reversed on would not understand either whence arose the attachment of men or life, nor above all how it could continue, threatened as it is at every moment by the facts. It is true that pessimists explain the persistence of this phenomnenon by the illusions of hope.