It is difficult --- perhaps impossible --- for a writer to say anything about his own work. All he has to say has been said as fully and as well as he can in the body of the book itself. If he has failed to make his meaning clear there it is scarcely likely that he will succeed in some pages of preface of postscript. And the author's mind has another peculiarity which is also hostile to introductions. It is as inhospitable to its offspring as the hen sparrow is to hers. Once the young birds can fly, fly they must; and by the time they have fluttered out of the nest the mother bird has begun to think perhaps of another brood. In the same way once a book is printed and published it ceases to be the property of the author; he commits it to the care of other people; all his attention is claimed by some new book which not only thrusts its predecessor from the nest but has a way of subtly blackening its character in comparison with its own.
--- From "An Introduction to