Because the world of learning within the geography of the Dutch Republic wascharacterized by dynamic patterns of migration, and because only a small minority of scholars corresponded in Dutch, the question arises whether there was any such thing as a ‘Dutch’ province within the international learned community. To what extent were scholars who corresponded from within the geographical coordinates of the United Provinces transnational in their epistolary contacts? We propose to measure and compare the strength of foreign relations by analysing correspondence traffic. We use epistolary networks as approximations of social networks, although the former is but a small part of the latter. Our analysis shows that the most active letter-writers had a nearly even ratio of foreign and Dutch correspondents and that foreign cities featured prominently in the intellectual geography of the Dutch Republic.