It is commonly assumed that the Formula of Reunion (433) marked the formal reception of Cyril of Alexandria's council of 431. In fact, not only did the terms of the Peace fall short of an explicit recognition of that gathering, but a vocal and organised group of bishops continued to resist its conciliar authority. These ‘irreconcilables' have tended to be overlooked - seen as representing a political and doctrinal ‘dead end', whose cause was decisively snuffed out in the wave of imperial exiles of 434-436. In their extant writings, however, we discover a significant and creative contribution to the articulation of ‘orthodoxy' in the years after Ephesus - a striking ‘minority report' that associated true fidelity to the Nicene faith with the rejection, rather than the acceptance, of Cyril's council. The paper will examine the contribution of one of these men - Eutherius of Tyana - to this alternative ‘idea of Nicaea'. It will note especially: (1) Eutherius' development of Nestorius' arguments against Cyril's interpretation of the Nicene Creed; (2) Eutherius' use of Cyril's conciliar documentation to undermine Cyril's own account of his council; (3) Eutherius' alternative narrative of Nicene orthodoxy, in which the Nicene faith was preserved and passed on not via the great conciliar consensus of Ephesus I, but rather via a faithful remnant who stood firm, contra mundum. In these ways, we are alerted to the remarkable flexibility of discourse concerning ‘orthodoxy' in this crucial decade.