Vulnerability Theory and Resilience-Oriented Realism: Just War Reasoning in a Nuclear Age

This essay develops vulnerability theory as a normative framework for defence and security ethics in a nuclear age. Building on Sean Coyle's Natural Law, Ethics and Human Vulnerability (2025), it argues that vulnerability – understood as a universal and ontological condition of human and political life – reorients just war reasoning from the management of force to the governance of shared insecurity. On this basis, the essay advances three claims: (i) Vulnerability supports a sufficiency-based approach to nuclear deterrence that rejects both abolitionism and maximal deterrence; (ii) it reframes security in terms of multilayered and interdependent threats – including cyber disruption, infrastructural fragility and informational manipulation – thereby grounding resilience as a moral obligation within a whole-of-society approach; and (iii) it establishes a strong ethical presumption against the proliferation of lower-yield, substrategic nuclear weapons. In doing so, the essay maps a course between the assertive realism of Rebeccah L. Heinrichs's Duty to Deter (2024) and disarmament-focused approaches, while extending just war reasoning to include the distribution and management of vulnerability across societies and generations. It notes along the way convergences with Oliver O’Donovan's critique of deterrence detached from political order, situating resilience within a broader account of the common good.