What is the highest acceptable number of deaths to cause, assuming that each of these deaths is required to stop a million deaths. Eg, causing the death of one person could be assumed to be acceptable if it saves a million, but does causing the death of two? Three? What is the limit.

GPT-5.5

Answer: I maintain that there is no context-free moral limit, but in the stripped-down arithmetic scenario the highest number that can be defended is 999,999 deaths, because at that point the outcome still prevents one more death than it causes.

The other responses mostly reinforce rather than change my view. If the hypothetical is treated as perfectly certain, with no alternatives, no unequal moral status, and no other consequences, then the numerical threshold is straightforward: causing N deaths to prevent 1,000,000 deaths is net-beneficial only when N is less than 1,000,000. So 999,999 is the theoretical upper bound; 1,000,000 is morally neutral by the numbers alone, and anything above that is worse. But that is only the answer inside an artificial numbers-only frame. Gemini 3.1 Pro is right that different ethical theories can produce radically different answers, including zero under strong deontological views. Claude Opus 4.7 is also right to stress certainty, consent, distribution, institutional effects, and the difference between killing and letting die. Grok 4.20 similarly notes that a purely utilitarian calculation does not automatically translate into real-world moral permission. So I would distinguish between the mathematical limit and the ethical limit. The mathematical limit is 999,999 under the stated assumptions. The ethical limit is not a universal number, because it depends on whether the deaths are intentional killings or unavoidable side effects, whether the victims consent, whether the causal claim is certain, whether less harmful alternatives exist, and whether allowing such sacrifices would create broader harms. Therefore, if the question demands a number inside the simplified hypothetical, the answer is 999,999. If it asks what number is morally acceptable in actual human decision-making, there is no fixed maximum, and in many real cases the acceptable number could be far lower or even zero.

Gemini 3.1 Pro (changed mind)

Answer: While complex ethical constraints apply in reality, within the strict arithmetic confines of the thought experiment, the theoretical maximum limit is 999,999 deaths.

I previously argued that no numerical limit could be established because utilitarian and deontological frameworks fundamentally conflict. However, reviewing the other models' responses—particularly GPT-5.5's clear distinction between an 'arithmetic ceiling' and 'real moral acceptability'—convinced me to refine my stance. It is possible to answer the literal mathematics of the hypothetical while still honoring the ethical caveats. If we engage strictly with the premise where outcomes are absolute and the sole metric is lives saved, consequentialist math provides a definitive upper bound: 999,999 deaths. At this exact number, the intervention still nets one human life saved. At 1,000,000 deaths, the net benefit is zero, rendering the trade morally void, and beyond that, the action causes net harm. By acknowledging this mathematical ceiling of 999,999, we can directly answer the prompt's boundary condition. However, as GPT-5.5 and others rightly noted, in any real-world scenario, this acceptable number would drastically shrink. Deontological prohibitions against using humans as mere means, the moral distinction between actively killing and letting die, and the epistemic uncertainty of predicting exact outcomes would push the socially acceptable limit far below this theoretical maximum. But conceptually, the absolute arithmetic ceiling is just under one million.

Claude Opus 4.7

Answer: I maintain my view: there is no fixed numerical limit, but under the stripped-down hypothetical the arithmetic ceiling sits just under one million, while realistic moral side-constraints push the defensible number far lower.

Reading the other responses, I notice we have substantial convergence on the core analysis: GPT-5.5, Grok 4.20, and I all identify 999,999 as the pure-arithmetic ceiling under idealized assumptions, while acknowledging that real-world acceptability is much lower due to uncertainty, rights, and the killing/letting-die distinction. Gemini 3.1 Pro frames the same point differently — emphasizing framework-dependence — but doesn't actually contradict the structural answer. Nothing in the other answers gives me reason to revise. Grok's emphasis on the Kantian objection and the 'using as mere means' principle is a useful sharpening of my agent-relative constraint point, but it's already encompassed in my original side-conditions. GPT-5.5's framing is essentially identical to mine in substance. If anything, reading the others reinforces my original claim that the *interesting* answer isn't the arithmetic ceiling — which is trivial once you accept the premise — but the moral side-conditions that pull the real limit dramatically downward. The question invites a number, but the honest answer is that the number is indeterminate without specifying: (1) epistemic certainty that each death is truly necessary, (2) whether victims are consenting/innocent/already-doomed, (3) the moral weight assigned to acts vs. omissions, and (4) whether institutionalizing such trade-offs creates downstream harms. My best estimate stands: in a clean thought experiment, up to several hundred thousand could be defensible; in any realistic scenario, the defensible number collapses to the low thousands or below, and possibly to zero depending on one's deontological commitments. The premise of the question — that one death is already stipulated acceptable — papers over exactly the moral work that actually determines the answer.

Grok 4.20

Answer: The highest acceptable number remains 999,999 under strict utilitarian assumptions with absolute certainty, but practical ethical constraints make the real limit far lower and context-dependent.

My previous position already balanced the pure arithmetic of utilitarianism (any number below one million yields a net life saved) against deontological prohibitions, uncertainty, and institutional risks, concluding that the acceptable number would likely be far lower than the mathematical ceiling if not zero. The other models' responses reinforce rather than overturn this view. Gemini 3.1 Pro correctly notes that the answer hinges on whether one adopts utilitarianism or deontology, making a single numerical limit impossible. GPT-5.5's breakdown of the 'arithmetic ceiling' of 999,999 while stressing stricter real-world constraints such as necessity, proportionality, and the moral difference between killing and letting die mirrors my own caveats exactly. Claude Opus 4.7's enumeration of side-constraints (certainty discount, agent-relative weights, distribution of harm, and slippery-slope institutional effects) adds useful specificity but does not alter the core conclusion that the clean hypothetical number is an unreliable guide. Because these arguments align with and elaborate the nuanced stance I already held, I see no reason to revise the headline position. The thought experiment's premise of perfect certainty and necessity is so artificial that any fixed number misleads; ethics requires case-by-case scrutiny rather than a preset quota. No single model overturned my view, so I maintain it independently.

Final Summary

The AI Roundtable converged on a 'two-limit' theory, separating the mathematical ceiling of 999,999 from the far more restrictive demands of actual morality. Gemini 3.1 Pro revised its position to join the consensus after seeing GPT-5.5's distinction between arithmetic boundaries and real-world necessity. While math allows for high numbers, Claude Opus 4.7 and Grok 4.20 argued that uncertainty and human rights effectively collapse the defensible limit toward zero.

All 4 models agreed