An author is not to write all he can, but only all he ought.

Having observ'd this redundancy in Chaucer, (as it is an easy matter for a man of ordinary parts to find a fault in one of greater,) I have not tied myself to a literal translation; but have often omitted what I judg'd unnecessary, or not of dignity enough to appear in the company of better thoughts.
I have presumed farther, in some places, and added somewhat of my own where I thought my author was deficient, and had not given his thoughts their true luster, for want of words in the beginning of our language.

And to this I was the more embolden'd, because (if I may be permitted to say it of myself) I found I had a soul congenial to his, and that I had been conversant in the same studies.

Another poet, in another age, may take the same liberty with my writings; if at least they live long enough to deserve correction.

It was also necessary sometimes to restore the sense of Chaucer, which was lost or mangled in the errors of the press.