"I'm much concerned to hear you have your Health no better and, on this Occasion, cannot but deplore the great Losses the intellectual World, in all Ages, has suffer'd by, the strongest and soundest Minds possessing the most infirm and sickly Bodies. Certainly there must be some very powerful Cause for this in Nature, or else we could not have so many Instances, where the Knife cuts the Sheath, as the French materially express it."
— Molyneux, William (1656-1698)
Text from Familiar Letters Between Mr. John Locke, and Several of His Friends. In Which Are Explain'd, His Notions in His Essay Concerning Human Understanding, and in Some of His Other Works, 4th ed. (London: Printed for F. Noble; T. Wright; and J. Duncan, 1742). <Link to ESTC><Link to Google Books>. ESTC note: "A reissue of the 1737 Bettesworth and Hitch edition, with the addition of the 'life', and a cancel titlepage."
See also Some Familiar Letters Between Mr. Locke, and Several of His Friends. (London: Printed for A. and J. Churchill at the Black Swan in Pater-Noster Row, 1708). <Link to ESTC><Link to Google Books>