Overture

In the late 1950s a London University student, Margaret Nickson, embarked on postgraduate research on a thirteenth-century Austrian inquisitor's treatise. After completion of her doctorate she got a job in the British Library, which was then located in the British Museum in Great Russell Street. One day she was leafing through one of the library's eighteenth-century catalogues and came across an astonishing entry. As she knew from her postgraduate days, one of the most important of all records of medieval heresy and inquisition was the massive Liber (Book) containing the sentences delivered in Toulouse between 1308 and 1323 by the inquisitor Bernard Gui. And one of the most famous stories was its fate. Although the manuscript had long since been lost its contents at least had been preserved, thanks to an edition printed in 1692. But what Nickson was reading contradicted the first part of this. The catalogue said the manuscript was in the British Library. She recounted what followed in the British Museum café in the late 1960s. She had run to the Manuscripts Room, quickly filled out an order slip and then counted the minutes. And then there it was, in front of her.

In the article she wrote on the manuscript's history she made particular use of John Locke's correspondence and journal in an account of the book's progress through the 1670s–90s. The protagonists were the Dutch Protestant theologian Philip van Limborch and Locke himself, two good friends who played crucial roles in the production of each other's work. Limborch helped Locke to get the first edition of his Letter on Toleration printed in Gouda in 1689. In turn Locke dedicated the Letter to Limborch and helped him with Gui's manuscript. Locke had known of it for many years and he played a leading role in bringing about what happened: the edition of Gui's Liber as an appendix to Limborch's Historia inquisitionis in 1692.

The concerns of this book are encapsulated here. In the early fourteenth century Gui's sentences had contained and constructed a certain sort of knowledge about people the Church labelled and persecuted as heretics.