When people talk as if the Crusades were nothing more than an aggressive raid against Islam, they seem to forget in the strangest way that Islam itself was only an aggressive raid against the old and ordered civilization in these parts. I do not say it in mere hostility to the religion of Mahomet; I am fully conscious of many values and virtues in it; but certainly it was Islam that was the invasion and Christendom that was the thing invaded.
To do Mohammed justice, his main attack was against the idolatries of Asia. Only he thought, just as the Arians did and just as the Unitarians do, that he could attack them better with a greater approximation to plain theism. What distinguishes his heresy from anything like an Arian or Albigensian heresy is that, as it sprang up on the borders of Christendom, it could spread outwards to a barbaric world.
