Amidst recent explorations in conciliar theology by Timothy Pawl and others, pressing questions about our theological readings of the councils have arisen – are we to treat the theology of the councils as unique to their historical context? Or as a unified body of ‘conciliar’ theology? This paper addresses these questions, using Eusebius of Caesarea as a unique example of Nicene theology. It defines the metrics for evaluating different definitions of the term ‘Nicene’ by distinguishing between judgements and concepts. Then, it ‘measures’ Eusebius’ theology according to the two proposed definitions. Finally, it offers constructive comments for conciliar theology, claiming that conceptual language is clarified through the councils, even if its interpretation is not immediately fixed.