Department or Program



This thesis traces the early modern intellectual lineages of Mare Liberum, the idea that the ocean should be common to all, and Mare Clausum, the idea that the ocean can be owned. It examines the genesis of Mare Liberum in jurist Hugo Grotius’s Mare Liberum as well as the genesis of Mare Clausum in eminent and well-developed responses to Grotius: William Welwod’s De Dominio Maris, Serafim de Freitas’s Do Justo Império Asiático dos Portugueses, and John Selden’s Mare Clausum: Of The Dominion, or, Ownership of the Sea. In bringing each theorist into dialogue and debate with the others, this thesis bridges language barriers and demonstrates the importance of understanding each theorist in his context. Ultimately, it argues that the continued existence of Mare Liberum and Mare Clausum as distinct “genealogies” of ideas centered on the fact that Grotius justified Mare Liberum on a philosophical level while jurists like Welwod, de Freitas, and Selden justified Mare Clausum on a practical level. With justifications resting in two separate spheres – one regarding what the nature of the ocean was and one regarding what the state of the ocean ought to have beenMare Liberum and Mare Clausum were unable to speak discursively to one another. In the early seventeenth century, Mare Clausum and Mare Liberum were ships passing in the night.

Level of Access

Open Access

First Advisor

Melvin, Karen

Date of Graduation


Degree Name

Bachelor of Arts

Number of Pages


Components of Thesis

1 pdf file

Open Access

Available to all.