In short this sort of vague evolutionary theorising simply amounts to finding an unconvincing explanation of something that needs no explanation.

And the case is really quite as simple with great political and religious movements by which man has from time to time changed the world in this or that respect in which he happened to think it would be the better for a change.
The Crusade was a religious movement, but it was also a perfectly rational movement; one might almost say a rationalist movement.
I could quite understand Mr.Pound saying that such a campaign for a creed was immoral; and indeed it often has been, and now perhaps generally is, quite horribly immoral.

But when he implies that it is irrational he has selected exactly the thing which it is not.
It is not enlightenment, on the contrary it is ignorance and insularity, which causes most of us to miss this fact.

But it certainly is the fact that religious war is in itself much more rational than patriotic war.
I for one have often defended and even encouraged patriotic war, and should always be ready to defend and encourage patriotic passion.
But it cannot be denied that there is more of mere passion, of mere preference and prejudice, in short of mere personal accident, in fighting another nation than in fighting another faith.
The Crusader is in every sense more rational than the modern conscript or professional soldier.

He is more rational in his object, which is the intelligent and intelligible object of conversion; where the modern militarist has an object much more confused by momentary vanity and one-sided satisfaction.
The Crusader wished to make Jerusalem a Christian town; but the Englishman does not wish to make Berlin an English town.
He has only a healthy hatred of it as a Prussian town.
The Moslem wished to make the Christian a Moslem; but even the Prussian did not wish to make the Frenchman a Prussian.
He only wished to make the Frenchman admire a Prussian; and not only were the means he adopted somewhat ill-considered for this purpose, but the purpose itself is looser and more irrational.
The object of all war is peace; but the object of religious war is mental as well as material peace; it is agreement.
In short religious war aims ultimately at equality, where national war aims relatively at superiority.