Apart from the four years that Barrow spent traveling abroad, his entire adult life was linked with Cambridge. Even as a traveler in distant lands his close association with his alma mater was apparent: While other travelers toasted their mistresses, Barrow drank to Trinity College. To understand the diverse concerns that shaped Barrow's work we must therefore know something of the academic milieu in which he lived and moved. This is particularly true since Barrow was associated with Cambridge in one of the most turbulent periods of the university's history. In the years between Barrow's matriculation at Peterhouse in 1643 and his death in 1677 Cambridge underwent a number of upheavals that were to affect its political and religious character as well as its standing in the eyes of the larger community.

In the first place, Cambridge was under parliamentary rule from virtually the beginning of the Civil War. Cromwell occupied it in 1642; in the following year many of its “monuments of superstition or idolatry” were destroyed, and in 1644–5 there was a wholescale purge of its members following the imposition of the Covenant, a declaration of support for an antiepiscopal church order. This purge resulted in the ejection of 217 dons (about half the fellowship of the university) and their replacement by those who were more sympathetic to the parliamentary regime. This purge was later followed by a more minor culling of dons following the Engagement of 1650, an oath of loyalty to the “Commonwealth of England, as the same is now established, without a King or a House of Lords.” At least forty-seven fellows (and possibly as many as fifty-six) were ejected.