The interpretation of differentia during late antique and early christian thought
Logic has often made major progress in historical circumstances that invited fierce debate and confrontation. The development of Christian thought during periods of crisis in the Church is no exception to this rule. This project explores for the first time how the philosophical notion of the differentia, a crucial term in the construction of definition in ancient logic, penetrated Christian thought and became the cardinal idea for the determination of orthodoxy during the theological debates about the nature(s) of Christ in the sixth and seventh centuries of our era, following the Council of Chalcedon (451 CE). 

The standard account explains these debates in terms of different interpretations of what it means for something to exist. The proposed project argues that the differentia came to be regarded as the condition of the possibility for existence as such, as the theologians improved the sophistication of their controversies by adopting and developing the terms of a logical debate among Neoplatonists in late antiquity. The theological debate on the reality and number of the nature(s) of Christ will be seen to rest on the opposition between interpreting the differentia as a real feature of reality–as the Chalcedonians did, or as merely a concept–which is the anti-Chalcedonian position. 

Designed as an interdisciplinary study of the interpretations and the evolution of the notion of the differentia, this project will disclose unknown chapters in the history of both theology and philosophy. At the same it will provide further support for the thesis that doctrinal wars outside philosophy were indeed waged, and settled, by adopting and developing the tools of logic. This strategy may well hold a promise for the doctrinal wars of the present, as well as for new developments in philosophy and logic.