William Duff seems to have spent his entire life in Aberdeenshire, where he was born, and where he died on 23 February 1815. He attended Marischal College, Aberdeen, from which he received his MA. In 1755 he obtained his licence to preach and was ordained on 8 October, when he took up a post in Glenbucket. Eleven years later, on 24 October 1766, he was transferred to Peterculter. In 1774, he went to Foveran, where he remained for the rest of his life, being instrumental in building a new church there in 1794. In Foveran he married, on 4 September 1778, Ann Mitchell; the couple had two sons and four daughters.
From The Continuum Encyclopedia of British Philosophy in Oxford Reference.