Anyway, below is a portion of the letter (27 October, 1786) Percival sent to Franklin that illustrates the subcultural zeitgeist in which Franklin was imbibed.
Dr. and Mrs. Priestley have been here this summer, together with Dr. Kippis. Dr. Priestley is not in a very good state of health, having had a return of the complaint with which he was visited several years ago; but his spirits and ardor do not desert him. He is at this time zealously engaged in attempts to convert the Jews to Christianity. For this undertaking he believes himself peculiarly well fitted, as it is a part of his creed, that Jesus Christ was the actual son of Joseph, and a lineal descendant of the house of David. But the Jewish rabbis have declared their resolution to enter into no discussion on these topics, being forbidden, as they allege, by their most sacred laws.
Dr. Kippis is busied with the Life of Captain Cook, which is to be published separately, as well as in the Biographia Britannica. Our excellent friend, Dr. Price, is, I hear, deeply affected with the death of his wife. A fresh paralytic stroke carried her off about a month since. The Doctor is preparing for the press a volume of Sermons in support of the Arian doctrine, and an enlarged edition of his valuable "Review of the Principal Questions and Difficulties in Morals." The College of Physicians in London have just printed a specimen of a new Pharmacopctia. The President has favored me with a copy; and I think the Dispensatory, on the whole, is likely to be much improved.