Risk and resilience for unknown, unquantifiable, systemic, and unlikely/catastrophic threats

Risk and resilience are important paradigms for analyzing and guiding decisions about uncertain threats. Resilience has sometimes been favored for threats that are unknown, unquantifiable, systemic, and unlikely/catastrophic. This paper addresses the suitability of each paradigm for such threats, finding that they are comparably suitable. Threats are rarely completely unknown or unquantifiable; what limited information is typically available enables the use of both paradigms. Either paradigm can in practice mishandle systemic or unlikely/catastrophic threats, but this is inadequate implementation of the paradigms, not inadequacy of the paradigms themselves. Three examples are described: (a) Venice in the Black Death plague, (b) artificial intelligence (AI), and (c) extraterrestrials. The Venice example suggests effectiveness for each paradigm for certain unknown, unquantifiable, systemic, and unlikely/catastrophic threats. The AI and extraterrestrials examples suggest how increasing resilience may be less effective, and reducing threat probability may be more effective, for certain threats that are significantly unknown, unquantifiable, and unlikely/catastrophic.