Which sentence in this excerpt from g. k. chesterton's "the fallacy of success" contains the central idea of the essay?

on every bookstall, in every magazine, you may find works telling people how to succeed. they are books showing men how to succeed in everything; they are written by men who cannot even succeed in writing books. to begin with, of course, there is no such thing as success. or, if you like to put it so, there is nothing that is not successful. that a thing is successful merely means that it is; a millionaire is successful in being a millionaire and a donkey in being a donkey. any live man has succeeded in living; any dead man may have succeeded in committing suicide. but, passing over the bad logic and bad philosophy in the phrase, we may take it, as these writers do, in the ordinary sense of success in obtaining money or worldly position. these writers profess to tell the ordinary man how he may succeed in his trade or speculation—how, if he is a builder, he may succeed as a builder; how, if he is a stockbroker, he may succeed as a stockbroker. they profess to show him how, if he is a grocer, he may become a sporting yachtsman; how, if he is a tenth-rate journalist, he may become a peer; and how, if he is a german jew, he may become an anglo-saxon. this is a definite and business-like proposal, and i really think that the people who buy these books (if any people do buy them) have a moral, if not a legal, right to ask for their money back. nobody would dare to publish a book about electricity which literally told one nothing about electricity; no one would dare to publish an article on botany which showed that the writer did not know which end of a plant grew in the earth. yet our modern world is full of books about success and successful people which literally contain no kind of idea, and scarcely any kind of verbal sense.