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Question

What is the principle of comparable sacrifice in ethics?

A look at the moral principle that obligates you to prevent great harm to a stranger whenever doing so costs you little.

Updated

The short answer

The principle of comparable sacrifice holds that if you can prevent something very bad from happening to someone without sacrificing anything of comparable moral significance, you are obligated to prevent it. This obligation holds regardless of your relationship to the person, their distance from you, or whether they could ever repay you. It is used to explain everyday duties, like helping someone in an emergency, as well as more demanding acts, like donating an organ to a stranger.

Key points

  • The principle obligates you to prevent severe harm whenever doing so does not require a comparably significant sacrifice from you.
  • It is a form of impartial morality: kinship, proximity, and the possibility of reciprocation do not change what you owe someone.
  • In a conversation on Hi-Phi Nation, Kieran Setiya uses the principle to explain both small acts, like calling for help, and large ones, like donating a kidney to a stranger.
  • The principle is not a demand for unlimited self-sacrifice, because it only applies when the cost to you is not itself comparable to the harm prevented.
  • The discussion frames the principle as a response to the puzzle of why humans sometimes help strangers in ways that evolutionary accounts of kin-favoring altruism do not predict.

The longer answer

The principle says nothing about how you feel toward the person you might help. It asks only two things: how bad is the outcome you could prevent, and how much would preventing it cost you. If the harm is severe and the cost to you is small by comparison, you are obligated to act. It does not matter whether the person in danger is your neighbor, a stranger on the other side of the world, or someone you will never meet.

This is worth pausing on, because most of our moral instincts run the other way. We treat family and friends as owed more than strangers. We treat people nearby as more urgent than people far away. We treat reciprocity, the sense that someone might one day help us back, as part of what makes helping make sense. The principle of comparable sacrifice cuts through all of that. It is a form of impartial morality: your relationship to the person, their distance from you, and whether they can ever repay you are not supposed to change what you owe them.

In a discussion on Hi-Phi Nation, the philosopher Kieran Setiya uses the principle to explain both ordinary and extraordinary cases. Calling for help when you see someone collapse on the street costs you almost nothing and could save a life, so the principle says you must do it. Donating a kidney to a stranger costs you a great deal more, but if the alternative is that person's death or years of suffering on dialysis, the same logic can be extended to justify the sacrifice. The conversation frames this as one of the puzzles at the heart of human altruism: people do make sacrifices for strangers that look nothing like the kin-favoring, reciprocity-tracking behavior that evolutionary accounts of altruism predict, and the principle of comparable sacrifice is one way philosophers have tried to state what those people are actually responding to.

The common misreading is to treat this as a demand for constant heroic self-sacrifice, as though morality now requires you to give away everything you have to help everyone you could possibly help. That is not what the principle says. It has a built-in limit: the sacrifice asked of you has to be comparable, not greater, than the harm you would prevent. You are not required to give up your career to save a stranger a mild inconvenience, and you are not required to bankrupt yourself for a marginal improvement in someone else's life. The principle scales. Small cost, large harm prevented: strong obligation. Large cost, small harm prevented: no obligation at all. The hard cases sit in between, where reasonable people disagree about what counts as comparable.

What changes if you take this seriously is not your feelings but your account of what you owe people you have no personal connection to. You cannot excuse inaction by pointing to distance or the absence of a relationship. If you would call an ambulance for a collapsed neighbor, and the only difference in a case abroad is geography, the principle asks you to notice that geography is not a moral reason to do less.

A concrete way to use it: before deciding whether you are obligated to help in a given situation, ask two separate questions rather than one. First, how bad is the outcome for the other person if you do nothing. Second, what would it actually cost you to prevent it, not what it feels like it would cost. Keeping those two questions separate, rather than letting the second one quietly answer the first, is most of what the principle asks of you.

Important distinctions

Comparable sacrifice versus unlimited self-sacrifice

The principle is often mistaken for a demand that you give everything you can to help anyone you can. It is not. The obligation only holds when the cost to you is small relative to the harm prevented. Once the cost to you becomes comparable to that harm, the obligation weakens or disappears. The principle scales with both variables, not just one.

Impartiality versus indifference to relationships

Treating a stranger's severe suffering as mattering as much as a neighbor's does not mean relationships count for nothing in every context. The principle addresses a narrow question: whether distance, kinship, or reciprocity change what you owe someone facing serious harm. It says they do not, without claiming that relationships are irrelevant to every other part of ethical life.

Objections and replies

The principle demands too much

If taken literally, the principle seems to require enormous sacrifices whenever the numbers work out, since there is almost always more good you could do for strangers if you gave up enough. Critics worry this makes ordinary life, with its own projects and attachments, morally impermissible.

Reply

The principle is self-limiting by design: it only asks for sacrifices that are not themselves comparable in significance to the harm prevented. The hard work is in deciding what counts as comparable, which is exactly where the disagreement in these cases tends to live.

It ignores how human altruism actually works

Evolutionary accounts explain helping behavior through kin selection and reciprocity, not impartial calculation of harms and costs. If human altruism evolved to favor family and reciprocal partners, a principle that ignores those categories may describe an ideal that has little to do with how people actually decide to help.

Reply

This is precisely the tension raised in the Hi-Phi Nation conversation: cases like kidney donation to strangers do not fit neatly into kin-selection or reciprocity models, which is why the principle of comparable sacrifice is offered as a way of describing what such donors seem to be responding to, whatever its evolutionary origins.

Related questions

Podcast discussions

Sources

  1. Hi-Phi Nation, The Selfless Kidney Donor Podcast episode, original episode