But, as Maine recognised, the acquisition of writing at the outset of national life is by no means sufficient to account for the progressiveness of the nations of South and Western Europe; we must seek other causes and conditions of their mental progress. We have already noted certain features of the racial constitution which were probably essential to the continued progress of the European peoples—namely, the high degree of evolution of the social disposition through group selection in the long prehistoric or race-making period; a group selection which probably was far more severe and prolonged than the peoples of any other part of the world were subjected to; and which in turn was due probably, as we have seen, to the great diversity of physical surroundings and to the comparative severity of the climate of Europe, especially of the northerly parts in which the most progressive European race was formed; for these physical conditions generated in the race an innate energy, a capacity for sustained effort. Without the highly developed social disposition in the mass of their members, primitive societies could not have survived those changes of custom and institution which were essential features of their progress. Without their innate energy, active rivalry and competition, which have been chief factors in social progress, would not have been constant features of the relations of these societies. Still the possession of a highly evolved social disposition by the European peoples does not in itself suffice to account for the continued mental evolution of the leading nations. For not all the European peoples have progressed; and, of those that have progressed, some have done so much more effectively than others. Let us first examine the question—In what has progress primarily consisted? Has it been primarily a progress of the moral or of the intellectual traditions? As I mentioned in an earlier chapter, we have here one of the main points of dispute.