Herein lies the main reason why the endeavor of the bourgeois Darwinists to defend the foundering capitalist system is bound to fail. Arguments based on natural science, when applied to social questions, must almost always lead to reverse conclusions. This happens because, while nature is very slow in its development and changes within the ken of human history are imperceptible, so that it may almost be regarded as stable, human society nevertheless undergoes quick and continuous changes. In order to understand the moving force and the cause of social development, we must study society as such. It is only here that we can find the reason of social development. Marxism and Darwinism should remain in their own domains; they are independent of each other and there is no direct connection between them. Here arises a very important question. Can we stop at the conclusion that Marxism applies only to society and that Darwinism applies only to the organic world, and that neither of these theories is applicable in the other domain? In practice it is very convenient to have one principle for the human world and another one for the animal world. In having this, however, we forget that man is also an animal. Man has developed from an animal, and the laws that apply to the animal world cannot suddenly lose their applicability to man. It is true that man is a very peculiar animal, but if that is the case it is necessary to find from these very peculiarities why those principles applicable to all animals do not apply to men, and why they assume a different form. Here we come to another grave problem. The bourgeois Darwinists do not encounter such a problem; they simply declare that man is an animal, and without further ado they set about to apply the Darwinian principles to men. We have seen to what erroneous conclusions they come. To us this question is not so simple; we must first be clear about the differences between men and animals, and then we can see why, in the human world, the Darwinian principles change into different ones, namely, into Marxism. VII. THE SOCIABILITY OF MAN. The first peculiarity that we observe in man is that he is a social being. In this he does not differ from all animals, for even among the latter there are many species that live socially among themselves. But man differs from all those that we have observed until now in dealing with the Darwinian theory; he differs from those animals that do not live socially, but that struggle with each other for subsistence. It is not with the rapacious animals which live separately that man must be compared, but with those that live socially. The sociability of animals is a power that we have not yet spoken of; a power that calls forth new qualities among animals.