In the first Part of this book we have reviewed the most general principles of collective mental life, beginning with the unorganised crowd as affording the simplest example, considering then an army as the simplest example of the profound modifications of collective mental life effected by organisation of the group. In the second Part we passed on to apply these principles to the understanding of the mind of the nation as the most important, complex, and interesting of all types of the group mind. In the third Part I take up the consideration in a general way of the processes by which national mind and character are gradually built up and shaped in the long course of ages. For, just as we cannot understand individual minds, their peculiarities and differences, without studying their development, so we cannot hope to understand national mind and character and the peculiarities and differences of nations, without studying the slow processes through which they have been built up in the course of centuries. In an earlier chapter, in connexion with the question of the importance of homogeneity of mental qualities as a condition of the existence of the national mind, I argued that race has really considerable influence in moulding the type of national mind. I recognized that differences of innate qualities between races, at any rate between allied subraces, are not great, and that they can be, and generally are, almost completely over-ridden and obscured in each individual by the moulding power of the social environment in which he grows up; but I urged that these racial qualities are very persistent, and that they exert a slight but constant pressure or bias upon the development of all that constitutes social environment, upon the forms of institutions, customs, traditions, and beliefs of every kind, so that the effect of such slight but constant bias accumulates from generation to generation, and in the long run exerts an immense influence. One way of treating the part played by the racial mental qualities in the development of the national mind would be to attempt to define the racial or innate peculiarities of the peoples existing at the present time, and to assume that these peculiarities were produced in the remote past, before the formation of nations began, and that they have persisted unchanged throughout the period of the development of nations. Something of this sort was proposed by Walter Bagehot in his _Physics and Politics_. He distinguished in the development of peoples two great periods—on the one hand the race-making period, which roughly corresponds to the whole prehistoric period, and on the other hand the nation-making period, which roughly corresponds to the historic period. This distinction has undoubtedly a certain validity.