Johnson was a seminal figure of American philosophy. Though busy with ministry and educational duties, and raising his family, he never stopped learning or writing, and kept to his self-appointed mission to write up the sum of all knowledge. In February 1729, Johnson noted in his "Autobiography", "came that very extraordinary genius Bishop Berkeley, then Dean of Derry, into America, and resided two years and a half at Rhode Island". Johnson hurried to visit him, and his group in Rhode Island, including the painter John Smybert. He became for a time a disciple of Berkeley's, and exchanged many letters with the philosopher over the years, discussing Berkeley's idealist philosophy. Before Berkeley left America in September 1731, Johnson convinced Berkeley to donate to Yale a large number of books, 500 pounds sterling, and a 100-acre farm with 100 pound sterling yearly income which would fund three scholars at the college.