First. In every particular state of the world, those nations which are strongest tend to prevail over the others; and in certain marked peculiarities the strongest tend to be the best. Secondly. Within every particular nation the type or types of character then and there most attractive tend to prevail; and, the most attractive, though with exceptions, is what we call the best character. Thirdly. Neither of these competitions is in most historic conditions intensified by extrinsic forces, but in some conditions, such as those now prevailing in the most influential part of the world, both are so intensified.
These are the sort of doctrines with which, under the name of 'natural selection' in physical science, we have become familiar; and as every great scientific conception tends to advance its boundaries and to be of use in solving problems not thought of when it was started, so here, what was put forward for mere animal history may, with a change of form, but an identical essence, be applied to human history. At first some objection was raised to the principle of 'natural selection' in physical science upon religious grounds; it was to be expected that so active an idea and so large a shifting of thought would seem to imperil much which men valued. But in this, as in other cases, the objection is, I think, passing away; the new principle is more and more seen to be fatal to mere outworks of religion, not to religion itself. At all events, to the sort of application here made of it, which only amounts to searching out and following up an analogy suggested by it, there is plainly no objection. Everyone now admits that human history is guided by certain laws, and all that is here aimed at is to indicate, in a more or less distinct way, an infinitesimally small portion of such laws. The discussion of these three principles cannot be kept quite apart except by pedantry; but it is almost exclusively with the first--that of the competition between nation and nation, or tribe and tribe (for I must use these words in their largest sense, and so as to include every cohering aggregate of human beings)--that I can deal now; and even as to that I can but set down a few principal considerations. The progress of the military art is the most conspicuous, I was about to say the most SHOWY, fact in human history. Ancient civilisation may be compared with modern in many respects, and plausible arguments constructed to show that it is better; but you cannot compare the two in military power. Napoleon could indisputably have conquered Alexander; our Indian army would not think much of the Retreat of the Ten Thousand. And I suppose the improvement has been continuous: I have not the slightest pretence to special knowledge; but, looking at the mere surface of the facts, it seems likely that the aggregate battle array, so to say, of mankind, the fighting force of the human race, has constantly and invariably grown. It is true that the ancient civilisation long resisted the 'barbarians,' and was then destroyed by the barbarians. But the barbarians had improved. 'By degrees,' says a most accomplished writer,[4] 'barbarian mercenaries came to form the largest, or at least the most effective, part of the Roman armies. The body-guard of Augustus had been so composed; the praetorians were generally selected from the bravest frontier troops, most of them Germans.' 'Thus,' he continues, 'in many ways was the old antagonism broken down, Romans admitting barbarians to rank and office; barbarians catching something of the manners and culture of their neighbours. And thus, when the final movement came, the Teutonic tribes slowly established themselves through the provinces, knowing something of the system to which they came, and not unwilling to be considered its members.' Taking friend and foe together, it may be doubted whether the fighting capacity of the two armies was not as great at last, when the Empire fell, as ever it was in the long period while the Empire prevailed. During the Middle Ages the combining power of men often failed; in a divided time you cannot collect as many soldiers as in a concentrated time. But this difficulty is political, not military. If you added up the many little hosts of any century of separation, they would perhaps be found equal or greater than the single host, or the fewer hosts, of previous centuries which were more united. Taken as a whole, and allowing for possible exceptions, the aggregate fighting power of mankind has grown immensely, and has been growing continuously since we knew anything about it.