Read it through once

At length the ancient system of religion and manners had fulfilled the circle of its revolutions. And the world would have fallen into utter anarchy and darkness, but that there were found poets among the authors of the Christian and chivalric systems of manners and religion, who created forms of opinion and action never before conceived; which, copied into the imaginations of men, become as generals to the bewildered armies of their thoughts. It is foreign to the present purpose to touch upon the evil produced by these systems: except that we protest, on the ground of the principles already established, that no portion of it can be attributed to the poetry they contain.