"A learned parson, rusting in his cell, at Oxford or Cambridge, will reason admirably well upon the nature of man; will profoundly analyze the head, the heart, the reason, the will, the passions, the senses, the sentiments, and all those subdivisions of we know not what; and yet, unfortunately, he knows nothing of man, for he hath not lived with him; and is ignorant of all the various modes, habits, prejudices, and tastes, that always influence and often determine him. He views man as he does colors in Sir Isaac Newton's prism, where only the capital ones are seen; but an experienced dyer knows all their various shades and gradations, together with the result of their several mixtures. Few men are of one plain, decided color; most are mixed, shaded, and blended; and vary as much, from different situations, as changeable silks do form different lights."
— Stanhope, Philip Dormer, fourth earl of Chesterfield (1694-1773)
Reading David Roberts' edition of Lord Chesterfield's Letters (Oxford: OUP, 1998); and searching text from Project Gutenberg <Link>
Consulting and citing, where possible, Letters Written by the late Right Honourable Philip Dormer Stanhope, Earl of Chesterfield, to his son, Philip Stanhope, Esq. (London: Printed for J. Dodsley, 1774). <Link to ECCO>
See also Miscellaneous Works of the late Philip Dormer Stanhope, Earl of Chesterfield: Consisting of letters to his Friends, never before printed, and Various Other Articles. 2 vols. (London: Printed for Edward and Charles Dilly, 1777). <Link to ECCO>