Philip Dormer Stanhope, Earl of Chesterfield 
Letters to His Son on the Art of Becoming a Man of the World and a Gentleman, 1750 [EPUB ebook] 

pub One.info present you this new edition. DEAR BOY: I have seldom or never written to you upon the subject of religion and morality; your own reason, I am persuaded, has given you true notions of both; they speak best for themselves; but if they wanted assistance, you have Mr. Harte at hand, both for precept and example; to your own reason, therefore, and to Mr. Harte, shall I refer you for the reality of both, and confine myself in this letter to the decency, the utility, and the necessity of scrupulously preserving the appearances of both. When I say the appearances of religion, I do not mean that you should talk or act like a missionary or an enthusiast, nor that you should take up a controversial cudgel against whoever attacks the sect you are of; this would be both useless and unbecoming your age; but I mean that you should by no means seem to approve, encourage, or applaud, those libertine notions, which strike at religions equally, and which are the poor threadbare topics of halfwits and minute philosophers. Even those who are silly enough to laugh at their jokes, are still wise enough to distrust and detest their characters; for putting moral virtues at the highest, and religion at the lowest, religion must still be allowed to be a collateral security, at least, to virtue, and every prudent man will sooner trust to two securities than to one