The dense marginal annotation made by freethinker, John Toland (1670–1722) and republican author and parliamentarian, Sir Robert Molesworth (1656–1725) on a copy of Martin Martin's Western Islands (1716) is an exceptional source for exposing the relationship between elite sociability and intellectual conversation. As an example of collaborative serial reading the case-study is unique, and allows a number of historical enquiries. Contextualizing Toland's and Molesworth's collaborative reading of the Royal Society sponsored work with the political and anticlerical projects both men pursued, the article argues that the surviving annotations are emblematic of the erudite, but still politically engaged, republic of letters of the period. Establishing the polemical engagement with clerical discourses about superstition, credulity, and ‘natural’ knowledge, by examining the literary, intellectual, and personal rhetoric at work in the marginalia, the article explores a case-study of cultural and intellectual debate at work in the early English Enlightenment.