Religious politics in Scotland during the middle decades of the seventeenth century have always attracted much historical attention. The conflict of the Covenant, the tensions of the Cromwellian occupation and the troubled Restoration period have understandably drawn scholars like moths to the flame. Many heroes have been discovered, ranging from Alexander Shields at one extreme to Archbishop James Sharp at the other, some of them with an apparent significance, intellectual or political, far beyond the supposedly purblind world of Restoration Scotland. But no contemporary has emerged more enhanced in the eyes of subsequent scholarship, nor more frustrated in his own time, than Robert Leighton – ‘the outstanding bishop of the period’ – bishop of Dunblane from 1661 to 1672 and for two more years the most reluctant archbishop of Glasgow ever to wear the mitre. A number of historians have trawled the evidence of a career which oscillated between failed attempts at accommodation between Episcopalians and Presbyterians and periods of disappointed withdrawal. His moderation and humanity, chief among the qualities noted by intimates such as Gilbert Burnet and opponents including Robert Wodrow, have inevitably loomed largest in most subsequent assessments of his actions. A few later scholars, particularly those strongly sympathetic to the Covenanters, have taken the opposite tack, regarding Leighton's excessive posthumous reputation as sufficient excuse for sometimes perverse contradiction. And yet the evidence offered by the celebrated library founded by the bishop in Dunblane has never been properly weighed. How far do the volumes accumulated during his lifetime and bequeathed to the Bibliotheca Leightoniana cast light upon its founder's philosophical interests? And do they help explain those peculiar responses, a remarkable commitment to both public reconciliation and private retirement, with which Leighton approached Scotland's troubled religious situation? These are the intertwined questions with which this essay is concerned.