 More’s interest in Descartes’s philosophy was so profound that his acquaintance, Samuel Hartlib (c.1600–1662), an assiduous “intelligencer” who keenly promoted (and facilitated) philosophical correspondence, persuaded More to write to Descartes in December 1648. More wrote four letters in all, but only received replies to the first two before Descartes’s death in 1650. He received an unfinished third reply from Claude Clerselier in 1655, while Clerselier was preparing his edition of Descartes’s Lettres (1657), which prompted More’s Responsio ad fragmentum Cartesii. It is clear from these letters that More’s differences with Descartes were (as we might expect) considerable and more serious than More realised.