The relatively scanty number of the human species rendered the strife for existence between man and man, even beyond the limits of association, less sharp, less continuous, and less necessary. At the same time, it must have greatly favored the development of sympathetic sentiments, and have left time for the discovery and appreciation of the utility of mutual support. In short, social life became the necessary condition of man's existence, in consequence of his capacity to modify his external surroundings and adapt them to his own wants, by the exercise of his primeval power in co-operation with a greater or less number of associates. His desires have multiplied with the means of satisfying them, and have become needs. And division of labor has arisen from man's methodical use of nature for his own advantage. Therefore, as now evolved, man could not live apart from his fellows without falling back into a state of animalism. Through the refinement of sensibility, with the multiplication of social relationships, and through habit impressed on the species by hereditary transmission for thousands of centuries, this need of social life, this interchange of thought and of affection between man and man, has become a mode of being necessary for our organism. It has been transformed into sympathy, friendship and love, and subsists independently of the material advantages that association procures. So much is this the case, that man will often face suffering of every kind, and even death, for the satisfaction of these sentiments. The fact is that a totally different character has been given to the strife for existence between man and man, and between the inferior animals, by the enormous advantages that association gives to man; by the fact that his physical powers are altogether disproportionate to his intellectual superiority over the beasts, so long as he remains isolated; by his possibility of associating with an ever increasing number of individuals, and entering into more and more intricate and complex relationships, until he reaches association with all humanity; and, finally, perhaps more than all, by his ability to produce, working in co-operation with others, more than he needs to live upon. It is evident that these causes, together with the sentiments of affection derived from them, must give quite a peculiar character to the struggle for existence among human beings.