In a vigorous theological controversy, William Bishop, English Roman Catholic theologian educated at Oxford, Rheims, Rome, and Paris, took on William Perkins, the best-selling English Protestant writer of the late sixteenth and early seventeenth centuries. The two writers were formidable champions of their respective religious traditions. As I will argue, this was a significant exchange, though the dispute has been little noticed by historians of the period. The issues the two writers discussed and the way they discussed them throw considerable light on the state of English religion in the early seventeenth century. Bishop emerges as a more powerful and effective spokesman for the Roman Catholicism of his day than has been heretofore recognised.

That King James I of England was ardently interested in religious ideas is well-known to students of the seventeenth century. Less well-known is the fact that he was specifically interested in the cause of religious reunion and played a leading part in a movement to find a way to reconcile the different national churches of his day and thus significantly to reduce international tensions. His plans did not exclude the possibility of a rapprochement between the Churches of the Reformation and Rome — even though James's own religious and political writings involved him in a series of bitter exchanges with leading Roman Catholic controversialists. From the beginning of his reign in England James had wanted to approach the problem of religious disunity through an international assembly of divines — or an ecumenical council, and he took care to make his intentions clear through diplomatic channels. During the years 1610–1614 he made use of the celebrated classical scholar Isaac Casaubon, then resident in England, in stimulating support for his ideas, especially in learned circles on the continent. Casaubon's death in England in the summer of 1614 deprived James of a zealous ally in the cause of Christian reunion, but it did not bring the campaign to which they had committed themselves to an end. By this time James was involved in the most ambitious reunion plan of his career, the result of his collaboration with Pierre Du Moulin, pastor of the Reformed Church in Paris and one of the leading theologians in France