John Dury (1596–1680) was one of Hartlib’s closest friends and collaborators from the late 1620s to the 1660s. Like Hartlib, he was deeply interested in the reform of education and philosophy, and committed to the cause of religious union among Protestants. Both men saw these as linked pursuits, in which the resolution of mental errors would contribute to the promotion of ecclesiastical peace and harmony, and direct the energy of Protestants into overcoming Roman Catholic power. In their hands, Baconian and Comenian philosophy became a weapon in the broader European conflict of the Thirty Years War, and a tool by which God’s people might achieve the overthrow of Antichrist.
The son of a Scottish minister, Dury had grown up in Leiden, and later served as chaplain to the English Company of Merchants at Elbing, where he may perhaps have encountered Hartlib for the first time. From 1628, when he first petitioned the Swedish king, Gustavus Adolphus, Dury travelled extensively in central and northern Europe, seeking to unite the various Protestant denominations in order to oppose the Catholic powers more effectively. His attempts to reconcile religious differences, in particular those between the Lutheran and Reformed Churches, were largely unsuccessful, although they did receive the support of a number of prominent churchmen, including several English bishops. In order to maintain support for Dury’s activities, Hartlib published an account of his travels and negotiations in 1641. This was addressed to the Long Parliament, in an attempt to win its aid and to encourage it to follow policies which might lead to evangelical union. It was also intended to clear Dury from the taint of Laudianism, and to demonstrate his commitment to the Protestant cause at a time when some Englishmen were tempted to interpret irenicism as a cover for Catholic plotting.