He censured on doctrinal lines the publication of George Bull's Harmonia Apostolica. He wrote much in this period, but published little. Mr. Cottington's Divorce Case, on which Barlow's reputation as an ecclesiastical lawyer and casuistic divine mainly rests, was written in 1671. Barlow was prominent in two abortive schemes of comprehension (inclusion into the state church) set on foot in October 1667 and February 1668. The "Comprehensive Bill", based on the Declaration of Breda, was drawn up by Sir Robert Atkyns and Sir Matthew Hale, and revised and endorsed by Barlow and his friend John Wilkins. Its introduction was frustrated by a Commons declaration and the plan was finally dropped. Barlow had some part in the release of John Bunyan from Bedford gaol in 1677. In 1675, Barlow became Bishop of Lincoln through the good offices of two secretaries of state, Sir Joseph Williamson and Henry Coventry, both graduates of Queen's College, the latter having been his pupil; Gilbert Sheldon was opposed. Barlow's consecration (on 27 June) did not occur in the customary Lambeth Chapel, but in the chapel attached to the Holborn palace of the Bishop of Ely (then Peter Gunning). George Morley of Winchester was the consecrating prelate. Barlow resided mostly at Buckden Palace, near Huntingdon, and was accused of never having entered his own cathedral. The Bishop's Palace at Lincoln had still not been repaired after the damage done in the English Civil War, although George Savile, 1st Marquess of Halifax remonstrated with Barlow on the subject in 1684. Barlow told his friend Sir Peter Pett that the real ground of hostility was not his avoidance of Lincoln, but his continuing hostility to Catholicism. In 1678, when Titus Oates forwarded his theory of a Popish Plot, Barlow had publicly declared enmity to the papists and their supposed leader, James, Duke of York. When the bill enforcing a test against popery was introduced, which excluded such peers from the House of Lords, Gunning of Ely defended the church of Rome from the charge of idolatry, but Barlow answered him vehemently. In 1680, while the Popish Plot panic was still at its height, he republished under the title of Brutum Fulmen, the papal bulls of Pius V and Paul III, pronouncing the excommunication and deposition of Queen Elizabeth and of Henry VIII, with inflammatory comments, and learned proofs that "the pope is the great Antichrist, the man of sin,