James Beattie's Theory of Language 1774

"Are then, all provincial accents equally good? By no means. Of accent, as well as cf spelling, syntax, and idiom, there is a standard in every polite nation. And, in all these particulars, the example of approved authors, and the practice of those, who by their rank, education, and way of life, have had the best opportunities to know men and manners, and domestick and foreign literature, ought undoubtedly to give the law.
Now it is in the metropolis of a kingdom, and in the most famous schools of learning, where the greatest resort may be expected of persons adorned with all useful and elegant accomplishments. The language, therefore, of the most learned and polite persons in london, and the neighbouring Universities of Oxford and Cambridge, ought to be accounted the standard of the English tongue, especially in accent and pronunciation: syntax, spelling, and idiom, having been ascertained by the practice of good authors, and the content of former ages."

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