18 ‘THE SHADOW OF THE WORLD’S FUTURE 
formed men are aware that fine characters are much 
alike and that all the anti-social elements in different 
countries are similar to each other. 
One sees then that, not only must Man face at once 
a study of the world’s possibilities of population, he 
must, as a part of this, face also the question of the 
migration of populations. This last reacts on the 
whole question. To ascertain how many human 
beings can ultimately live upon the earth, one has to 
postulate that all avoidable causes of variation in the 
density of population have been adjusted, as far as 
that is possible. This latter question is by no means 
a simple one. 
What has now been outlined reveals the importance 
and the urgency of a study of the World’s Future from 
many points of view, and we propose now to consider 
that future from the standpoint of population itself. 
Of all questions that challenge the attention of Man, 
this occupies a unique place, and the world’s statesmen 
are realising it.