To these questions I have no very satisfactory answers to give, nor do I believe that our knowledge of national or social psychology is sufficient to make a satisfactory answer possible. Some purely tentative observations on the point may, however, furnish a fitting conclusion to an address which has been tentative throughout, and aims rather at suggesting trains of thought, than at completing them. I assume that the factors which combine to make each generation what it is at the moment of its entrance into adult life are in the main twofold. The one produces the raw material of society, the process of manufacture is effected by the other. The first is physiological inheritance, the second is the inheritance partly of external conditions of life, partly of beliefs[2], traditions, sentiments, customs, laws, and organisation--all that constitute the social surroundings in which men grow up to maturity. I hazard no conjecture as to the share borne respectively by these two kinds of cause in producing their joint result. Nor are we likely to obtain satisfactory evidence on the subject till, in the interests of science, two communities of different blood and different traditions consent to exchange their children at birth by a universal process of reciprocal adoption. But even in the absence of so heroic an experiment, it seems safe to say that the mobility which makes possible either progress or decadence, resides rather in the causes grouped under the second head than in the physiological material on which education, in the widest sense of that ambiguous term, has got to work. If, as I suppose, acquired qualities are not inherited, the only causes which could fundamentally modify the physiological character of any particular community are its intermixture with alien races through slavery, conquest, or immigration; or else new conditions which varied the relative proportion in which different sections of the population contributed to its total numbers. If, for example, the more successful members of the community had smaller families than the less successful; or if medical administration succeeded in extinguishing maladies to which persons of a particular constitution were specially liable; or if one strain in a mixed race had a larger birth rate than another--in these cases and in others like them, there would doubtless be a change in the physiological factor of national character. But such changes are not likely, I suppose, to be considerable, except, perhaps, those due to the mixture of races;--and that only in new countries whose economic opportunities tempt immigrants widely differing in culture, and in capacity for culture, from those whose citizenship they propose to share.