Nathan Sears was one of seven to die in a fire in Montreal on the 16 March 2023. He was 35. 

Nathan was becoming a leading figure at the intersection of existential risk and international relations (IR). 

Indeed, he was in Montreal to attend the 2023 International Studies Association (ISA) conference, the leading conference on international relations (IR). The day before on March 15th, he presented a paper on "Great Power Rivalry and Human Survival: Why States Fail to “Securitize” Existential Threats to Humanity" at a panel on 'Catastrophic-Existential Risks and World Orders'

After his undergrad at Western University and his Masters in IR at Carleton University Nathan moved to Quito, Ecuador. For four years he taught IR at the Universidad de Las Américas. He then came back to Canada in 2016 to earn his PhD.

During that time he was a 2017-2018 Trudeau Centre Fellow in Peace, Conflict and Justice at the Munk School of Global Affairs. He also took a year out to serve his country as a 2019-2020 Cadieux-Léger Fellow in the Foreign Policy Research and Foresight Division of Global Affairs Canada.

Nathan was already an important scholar in the field of  existential risk, making groundbreaking & much-discussed contributions at the intersection with international relations. He was also a really friendly, supportive and engaging guy. I was so excited about what he was going to accomplish. 

Five of his most important papers are:

• International Politics in the Age of Existential Threats
  • Humans in the twenty-first century live under the specter of anthropogenic existential threats to human civilization and survival. What is the significance of humanity’s capacity for self-destruction to the meaning of “security” and “survival” in international politics? The argument is that it constitutes a material “revolution” in international politics—that is, the growing spectrum of anthropogenic existential threats represents a radical transformation in the material context of international politics that turns established truths about security and survival on their heads. The paper develops a theoretical framework based in historical security materialism, especially the theoretical proposition that the material circumstances of the “forces of destruction” determine the security viability of different “modes of protection”, political “units” and “structures”, and “security ideologies” in international politics. The argument seeks to demonstrate the growing disjuncture (or "contradiction") between the material context of anthropogenic existential threats ("forces of destruction"); and the security practices of war, the use of military force, and the balance-of-power ("modes of protection"); the political units of nation-states and structure of international anarchy ("political superstructure"); and the primacy of "national security" and doctrines of "self-help" and "power politics" in international politics ("security ideologies"). Specifically, humanity's survival interdependence with respect to an-thropogenic existential threats calls into question the centrality of national security and survival in international politics. In an age of existential threats, "security" is better understood as about the survival of humanity.
• Existential Security: Towards a Security Framework for the Survival of Humanity 
  • Humankind faces a growing spectrum of anthropogenic existential threats to human civilization and survival. This article therefore aims to develop a new framework for security policy – ‘existential security’ – that puts the survival of humanity at its core. It begins with a discussion of the definition and spectrum of ‘anthropogenic existential threats’, or those threats that have their origins in human agency and could cause, minimally, civilizational collapse, or maximally, human extinction. It argues that anthropogenic existential threats should be conceptualized as a matter of ‘security’, which follows a logic of protection from threats to the survival of some referent object. However, the existing frameworks for security policy – ‘human security’ and ‘national security’ – have serious limitations for addressing anthropogenic existential threats; application of the ‘national security’ frame could even exacerbate existential threats to humanity. Thus, the existential security frame is developed as an alternative for security policy, which takes ‘humankind’ as its referent object against anthropogenic existential threats to human civilization and survival. 
• Great Power Rivalry and Macrosecuritization Failure: Why States Fail to “Securitize” Existential Threats to Humanity.
  • Humanity lives under a growing spectrum of existential threats that have their origins in human agency and could bring about the collapse of modern global civilization or even human extinction. Why do states fail to mobilize the will and resources to neutralize the existential threats to humankind? This dissertation develops a theory of “macrosecuritization failure,” based on securitization theory and the concept of “macrosecuritization,” and studies the empirical phenomenon of the recurrent failure of states to take extraordinary action for the security and survival of humankind. It finds great power consensus or rivalry to be the central dynamic behind the success or failure of macrosecuritization in international relations. In the absence of a world political entity with the authority and capabilities to “speak” and “do security” on behalf of humanity, the great powers collectively shape the fate of macrosecuritization and the security of humankind. The argument is that conflicting security narratives of “humanity securitization” and "national securitization”—or ways of framing the referent object, the threat, and necessary measures for security—shape the thinking and action of the great powers towards macrosecuritization. When a security narrative of humanity securitization prevails, this can open space for great power consensus on macrosecuritizaton; but when national securitization triumphs, great power rivalries lead them to prioritize national power and security over the security and survival of humankind. The dissertation examines three historical case studies of macrosecuritization (failure) in international relations: the international control over atomic energy (1942-1946), the Biological Weapons Convention (1968-1972), and artificial intelligence (2014-present). The theoretical framework posits three variables to explain the influence of conflicting security narratives over the great powers: (1) the stability of the distribution of power in the international system; (2) the power and interests of domestic securitizing actors over state audiences; and (3) the beliefs and perceptions of political leaders about threats. Ultimately, macrosecuritization fails when these conditions favour a security narrative of national securitization amongst the great powers, whereby fear of “the Other” outweighs fear of an existential threat. The argument has important implications in an age characterized by the escalating great power rivalry between the United States and China under a growing spectrum of existential threats to humanity.
• Anarchy, Technology, and the Self-Destruction Hypothesis: Human Survival and the Fermi Paradox
  • Does the technological capability for "self-destruction" grow faster than the political capacity to control and restraint it? If so, then the uneven growth rates between technology and politics could provide a theoretical explanation for the "Fermi Paradox"-or the contradiction between the high probability of the existence of intelligent life, and the absence of empirical evidence for it "out there" in the universe. This paper postulates the anarchy-technology dilemma as a solution to the Fermi Paradox: in essence, intelligent civilizations develop the technological capability to destroy themselves before establishing the political structures to prevent their self-destruction.
• Great Powers, Polarity, and Existential Threats to Humanity: An Analysis of the Distribution of the Forces of Total Destruction in International Security
  • Which states possess the material capacity to destroy humanity? This paper develops a new framework for analysis of the "great powers" and the "structure" (or "polarity") of the system of international security, based on the distribution of the material capabilities that threaten humankind--or the "forces of total destruction." It argues that a state is a great power if it possesses national capabilities that constitute an existential threat to humanity. The empirical analysis measures the leading states in the international system--China, France, Germany, India, Japan, Russia, the United Kingdom, and the United States--against this standard for great power status with respect to three anthropogenic existential threats to humanity: nuclear war, climate change, and artificial intelligence. It finds that three states--China, Russia, and the United States--are great powers, and therefore the system is multipolar. It concludes with a discussion of the theoretical and practical implications of the analysis for our understanding of great power status, including the unequal power and differential responsibility of the great powers and the possibilities for "great power management" of existential threats in the twenty-first century.