I now come to what is by far the most arduous
portion of the task which I have set myself to perform. Indeed had I fully realised the difficulties
when I first designed this work, I should have considered betimes whether my strength was sufficient to
support the load that now weighs upon me so heavily.
But to begin with, I felt how shameful it would be
to fail to perform what I had promised, and later,
despite the fact that my labour became more and
more arduous at almost every stage, the fear of
stultifying what I had already written sustained my
courage through every difficulty.