CH. XX.] CONDITIONS OF PROGEESS. 263 



to me to Lave been the last of the great fights in which the 

 further continuance of European civilization was really 

 imperilled. Though the victory of Attila could hardly have 

 entailed the reharbarizing of the whole Empire, it might well 

 have caused such a temporary " solution of continuity" between 

 ancient and modern history as the old historians supposed to 

 have been wrought a few years later by the comparatively 

 insignificant intrigues of Odoacer. Many hard- working years 

 might have been needed to recover the ground thus lost. 

 But in passing to the eighth century, I think we may well 

 doubt the soundness of Gibbon's suggestion that the victory 

 of Abderahman at Tours might have led to the Moham- 

 medanization of Europe ; for while one great defeat forced the 

 Arab to retire behind the Pyrenees, on the other hand the 

 complete overthrow of the Frankish power would probably 

 have required many battles as fierce as this one. This 

 increased toughness of civilization is still more plainly seen 

 five centuries later, when the overwhelming victory of the 

 Mongols at Liegnitz produced no effect at all beyond a 

 temporary scare. It was not that the invasion under Batu 

 was intrinsically less formidable than the invasion of Attila, 

 but that the physical strength of civilized Europe had been 

 growing throughout the long interval, so that the blow which 

 might once have proved fatal was no longer dangerous. 

 Since the fruitless sieges of Vienna by the Turks, the mere 

 dread of barbaric or semi-barbaric invasion has passed away 

 for ever. Tribally-organized barbarism is henceforth out of 

 the lists entirely, and even the civilization of lower type has 

 ceased to compete, in a military way, with the civilization of 

 higher type. 



Thus we see how natural selection, facilitating and co- 

 operating with the integration of the more civilized communi- 

 ties and their increase in size and complexity, has gradually 

 removed one of the dangers to which the earlier civilizations 

 were exposed, and has concentrated the power of making 



