In the last thirty years of the eighteenth century, Rational Dissent's sense of collective identity became more sharply focused. This chapter identifies the theological opinions that united Rational Dissenters while simultaneously distinguishing them from Orthodox Dissenters. The first section explores those points of common agreement between Arians and Socinians through an analysis of sermons and letters. The second section moves to an examination of the impact of these shared doctrines upon practice through analyses of published hymn books, lists of subscribers to Rational Dissenting works and organisations, memoirs and newspapers, as well as unpublished diaries and letters. The third and fourth sections argue, respectively, that theology deeply affected all aspects of the lives and activities of Rational Dissenters; and that networks that were initially informal crystallised in the 1790s into more formal organisations that played a larger role in supporting and publicising Rational Dissent than has hitherto been acknowledged.

Central to the collective identity of Rational Dissent was a general agreement on the fundamental importance of the rational approach resting on the sole foundation of the Scriptures. When in 1774 the Unitarian minister John Disney wrote in a public letter to Frederick Cornwallis, archbishop of Canterbury, that:

– he implied that the Church of England had departed from these two key principles, principles that underpinned the theology of Orthodox as well as Rational Dissent. The rule of faith contained in the Scriptures was not only to be observed but, as far as possible, to be understood. Yet the observation of Michael Watts that ‘rational Arminianism was inclined to treat Christianity as a philosophy to be debated rather than a faith to be shared’ takes the concept of a dry rationality too far, as far as Rational Dissenters were concerned, and does not take sufficient account of the ‘rational piety’ of their worship as examined by R. K. Webb. Reason, rather than replacing the sharing of faith amongst them, helped to explain and sustain it.