Of the various systems of sociology that have been developed since the new "science" was first outlined by Auguste Comte, that of Herbert Spencer is undoubtedly the most coherent and self-consistent. But even the genius of Mr. Spencer has been unequal to the task of working out a body of firmly grounded principles which should furnish a basis for the convergence of opinion on social questions. He has not succeeded in giving permanent form and content to sociology. His work is disparagingly criticised by other living sociologists. Small declares that "Spencer's sociology ends precisely where sociology proper should begin," and quotes approvingly De Greef's assertion that "Mr. Spencer not only fails to show that there is a place for sociology, but his own reasoning proves more than anything else that there is no social science superior to biology."[37] Ward, while commending the logical consistency of Mr. Spencer's work, pronounces him "unsystematic, nonconstructive, and nonprogressive."[38] [Footnote 37: See Giddings. Principles of Sociology, chap. i.] [Footnote 38: Small and Vincent. Introduction to the Study of Society, p. 46]. There is much justice in these criticisms of Mr. Spencer's system. His sociology is almost entirely descriptive; and his description of social phenomena has taken the form of an elaborate analogy between society and the animal organism. The utility of this biological analogy has rightly been called in question. The particular resemblances traced by Mr. Spencer between a society and a living body are these: both grow and increase in size; while they increase in size they increase in structure; increase in structure is accompanied by progressive differentiation of functions; and differentiation of functions leads to mutual interdependence of the parts. Furthermore, in the case both of a society and of a living body the lives of the units continue for some time if the life of the aggregate is suddenly arrested; while if the aggregate is not suddenly destroyed by violence its life greatly exceeds in duration the lives of its units. Since, therefore, the permanent relations among the parts of a society are analogous to the permanent relations among the parts of an organism, society is to be regarded as an organism.