In 1681, prompted by the doubts raised by the Jesuit Daniel van Papenbroek over the authenticity of supposed Merovingian documents held at the Abbey of Saint-Denis, Mabillon published his De re diplomatica.
This work investigated different types of medieval documents and manuscripts, including scrutiny of their script, style, seals, signatures, testimonia, and other intrinsic and extrinsic factors, using an acquired taste derived from long experience, and consulting the views of other document scholars.
Manuscripts from many archives are addressed, and references made to items dating back to Dagobert I (King of the Franks, c.629-639).
Concerned often with "distinguishing genuine documents from forgeries" the work is now seen as the foundation work of palaeography and diplomatics.
Mabillon writes:
I do not deny that in fact some documents are false and others interpolated, but all of them should not be dismissed for that reason.
Rather, it is necessary to devise and hand down rules for distinguishing genuine manuscripts from those that are false and interpolated. ...
I undertook this task after long familiarity and daily experience with these documents.
For almost twenty years I had devoted my studies and energies to reading and examining ancient manuscripts and archives, and the published collections of ancient documents. ...
I compared and weighed them with one another that I might be able to compile a body of knowledge which was not merely scanty and meager, but as accurate and as well-tested as possible in a field which had not been previously investigated.

This work brought Mabillon to the attention of Jean-Baptiste Colbert, who offered him a pension (which he declined), and King Louis XIV.
He began to travel throughout Europe, to Flanders, Switzerland, Germany, and Italy, in search of medieval manuscripts and books for the royal library.
In 1681, prompted by the doubts raised by the Jesuit Daniel van Papenbroek over the authenticity of supposed Merovingian documents held at the Abbey of Saint-Denis, Mabillon published his De re diplomatica. This work investigated different types of medieval documents and manuscripts, including scrutiny of their script, style, seals, signatures, testimonia, and other intrinsic and extrinsic factors, using an acquired taste derived from long experience, and consulting the views of other document scholars. Manuscripts from many archives are addressed, and references made to items dating back to Dagobert I (King of the Franks, c.629-639). Concerned often with "distinguishing genuine documents from forgeries" the work is now seen as the foundation work of palaeography and diplomatics. Mabillon writes:
I do not deny that in fact some documents are false and others interpolated, but all of them should not be dismissed for that reason. Rather, it is necessary to devise and hand down rules for distinguishing genuine manuscripts from those that are false and interpolated. ... I undertook this task after long familiarity and daily experience with these documents. For almost twenty years I had devoted my studies and energies to reading and examining ancient manuscripts and archives, and the published collections of ancient documents. ... I compared and weighed them with one another that I might be able to compile a body of knowledge which was not merely scanty and meager, but as accurate and as well-tested as possible in a field which had not been previously investigated.
This work brought Mabillon to the attention of Jean-Baptiste Colbert, who offered him a pension (which he declined), and King Louis XIV. He began to travel throughout Europe, to Flanders, Switzerland, Germany, and Italy, in search of medieval manuscripts and books for the royal library.
Jean Mabillon