...I thank you, my dear Sir, for the volume you were so kind as to send me some time ago. Everything you write is precious, and this volume is on the most precious of all our concerns. We may well admit morality to be the child of the understanding rather than of the senses, when we observe that it becomes dearer to us as the latter weaken, & as the former grows stronger by time & experience till the hour arrives in which all other object lose all their value ... (TJ to Price, 11 July 1788)

http://lcweb2.loc.gov/cgi-bin/ampage?collId=rbc3&fileName=rbc0001_2007jeffca...