[2][3][4] In 1643 he was chosen university mathematical lecturer, but he was deprived of his fellowship next year for opposing the Solemn League and Covenant (with Isaac Barrow, John Barwick and Peter Gunning).

[4][5] In 1649, he became Savilian professor of astronomy at Oxford University, and gained a high reputation by his theory of planetary motion, propounded in the works entitled In Ismaelis Bullialdi astronomiae philolaicae fundamenta inquisitio brevis (Oxford, 1653), against the cosmology of Ismael Boulliau, and Astronomia geometrica (London, 1656) on the system of Kepler.

[2][6] About this time he was engaged in a decades-long philosophical controversy with Thomas Hobbes:[2][7] Seth Ward and John Wallis, both Savilian professors and members of the Anglican clergy, felt offended by the works of Hobbes, particularly after Leviathan was released.

[2] King Charles II appointed him to the livings of St Lawrence Jewry in London, and Uplowman in Devonshire, in 1661.

[2] In his diocese he showed great severity to nonconformists, and rigidly enforced the act prohibiting conventicles (unofficial religious meetings).