If one wishes to investigate the history of the development of an idea, two approaches are possible. One is to begin at the beginning, following the development step by step until one reaches the stage at which the idea attains its fullest flowering. The other approach is precisely the reverse. One chooses a point of departure in the final phase and then works backwards to the moment at which the idea first appeared. This latter method has many practical advantages in research. One can see the phenomenon in its most mature form, and thus more easily recognise its components and their earlier relationship.
When, some years ago, I decided to devote a lecture to eirenism in the sixteenth century, my preparation followed the second approach. I chose as my starting point the work of a renowned eirenist of a later generation, Hugo Grotius. Leafing through the fourth volume of the Basel edition of his Opera Theologica, my attention was drawn to an entry Via ad pacem ecclesiasticam. It proved to comprise a number of miscellaneous documents, some of them by Grotius himself, some of them his annotations on the work of others, and yet others evidently added to the dossier because they fitted into the framework of eirensim. I decided to delve more deeply into this collection, which was first published as a separate work in 1642.