Existential Terrorism: Can Terrorists Destroy Humanity?

Mass-casualty terrorism and terrorism involving unconventional weapons have received extensive academic and policy attention, yet few academics have considered the broader question of whether such behaviours could pose a plausible risk to humanity’s survival or continued flourishing. Despite several terrorist and other violent non-state actors having evinced an interest in causing existential harm to humanity, their ambition has historically vastly outweighed their capability. Nonetheless, three pathways to existential harm exist: existential attack, existential spoilers and systemic harm. Each pathway varies in its risk dynamics considerably. Although an existential attack is plausible, it would require extraordinary levels of terrorist capability. Conversely, modest terrorist capabilities might be sufficient to spoil risk mitigation measures or cause systemic harm, but such actions would only result in existential harm under highly contingent circumstances. Overall, we conclude that the likelihood of terrorism causing existential harm is extremely low, at least in the near to medium term, but it is theoretically possible for terrorists to intentionally destroy humanity.