Everyone has a theory. Few will name it.

You do not need a theory of ethics to notice that causing a great deal of suffering for a small pleasure needs some justification. But when someone says animals matter less, or that nature settles the question, or that there is no obligation to beings who cannot reciprocate, they are appealing to a framework. Naming it is usually enough to see whether the appeal works.

Each section below gives the core idea, where it lands on this question, and its honest difficulty. Where a framework offers genuine resistance, it is said plainly rather than waved away.

All five are theories about what you ought to do. The other common move in these arguments is to deny that there is anything to be right about: that morality is subjective, or cultural, or just how you feel. Those are claims about what a moral statement is rather than about what it requires, and they have a page of their own.

One warning before the list, because it is the objection a careful reader makes first. Each framework below starts from a premise it does not prove: that outcomes are what matter, or that some things may not be done whatever the outcome, or that morality is what we could agree to. Setting them out side by side can look like a menu, as though the honest thing were to pick the one you like. It is not, and the question of what would make any of them true rather than merely appealing is the hardest thing on this site. It is taken up at the end, and at more length on the other page.

Is morality just opinion?

Consequentialism is the belief that only outcomes decide whether an action is right. Not intentions, not rules, not what kind of person you are: just what happens as a result.

Utilitarianism is its best-known form, and the one almost everyone means when they argue this way. It says the outcome to measure is suffering and wellbeing, and that the right thing to do is whatever produces the best balance of them. Everyone affected counts, and nobody’s suffering counts for more because of who they are.

So the question to ask about any action is simple, even if answering it is not: who is affected, how badly, and is there a better option.

For veganismThe only thing that matters is whether a being can suffer, not whether it is clever, or human, or useful to us. This is the tradition Peter Singer wrote from in 1975, and it is where the word speciesism comes from: ignoring an interest because of what species it belongs to looks, from here, like the same mistake as ignoring it because of race or sex.

Where it landsStrongly against animal farming. The suffering is vast and well documented, the benefit is a taste preference, and a taste preference is not much weight to put on the other side of the scale.

Its difficultyThe same arithmetic can license uncomfortable conclusions elsewhere, since in principle any harm can be outweighed by enough benefit. People who reject utilitarianism usually reject it for that reason, not because of animals.

The argument inside itIt does not simply follow from utilitarianism that every animal counts the same. Many utilitarians distinguish a person, meaning a being aware of itself over time with preferences about its own future, from a being that can suffer but has no such plans. On that view a painless death wrongs the first by thwarting what it wanted and may not wrong the second at all, which leaves room to defend killing an animal that had a good life. Singer himself has argued over this for decades and his position has moved. So the framework rules out the suffering of factory farming very quickly, and the argument about killing carries on inside it rather than being settled by it.

This is the belief that some things may not be done to someone no matter how much good comes of it. Morality is a matter of duties and claims rather than of totals: you cannot justify using a person by adding up the benefits to everyone else.

Most people already think this about humans. We do not think one unwilling person may be harmed because five others would gain, however the arithmetic works out.

For veganismThe question becomes whether animals are the kind of being that can hold such a claim. Tom Regan argued that any being whose life matters to it cannot be treated as a resource, which rules animal use out altogether rather than merely regulating how it is done.

Where it landsAgainst animal use outright, and more firmly than utilitarianism does. It does not permit a trade in which the animal loses and the benefit is elsewhere, which is what farming is.

Its difficultyIt has to explain where rights come from, and why they extend to animals but, on most accounts, not to every living thing. That line is harder to draw than it looks.

Virtue ethics is the belief that the right question is not which rule applies or which outcome is best, but what a good person would do, and what doing a thing makes of the person who does it. Cruelty is wrong because it is what a cruel person does, and because indulging it shapes you.

For veganismIt asks what kind of person is comfortable paying for something they would not watch being done and would not do themselves.

Where it landsAgainst animal farming, but by a different route from the others. It never weighs the suffering against the pleasure at all.

Its difficultyThe least decisive of the frameworks, because what counts as virtuous is partly cultural, and in most cultures eating animals has never been treated as a vice. It is better at explaining why the practice feels wrong once you look at it than at proving that it is.

Contractualism is the belief that morality is whatever rules people could reasonably agree to for living alongside each other. Obligations hold between those able to take part in that agreement, and to hold each other to it.

It explains a lot of ordinary morality well: promises, fairness, and why we owe things to people we have never met but share a society with.

For veganismAnimals cannot take part in an agreement or be held to one, so on the face of it they fall outside the arrangement. This is the framework the hardest objections on this site are reaching for.

Where it landsThis is the framework that offers the most resistance to the case for veganism, and it is worth saying so rather than skipping past it.

Why it is not enoughThe same reasoning excludes infants, people with severe cognitive disabilities and future generations, and almost nobody accepts that. Once the framework is widened to include those cases, usually by including beings whose interests can be represented rather than asserted, animals come back inside it. Contractualists have answers here, and they are the most interesting part of the literature, but the ones that keep animals out tend to keep out people we are not willing to exclude.

Care ethics is the belief that morality starts from relationships and dependence rather than from principles. What matters is attending to those in our care and responding to need in front of us, which is closer to how most people actually make decisions than any rule is.

For veganismIt explains something the other frameworks struggle with: why someone who would never hurt a dog will happily pay for a pig to be killed. The difference is relationship and visibility, not anything about the animal.

Where it landsAgainst farming, once you notice that the difference is relationship and visibility rather than anything about the animal itself.

Its difficultyIf obligations track relationships, it is hard to explain what is owed to animals we will never meet. Taken alone it can justify the inconsistency it diagnoses.

Here is the objection that none of the five frameworks above can answer on its own. Every one of them begins somewhere it does not argue for. Consequentialism assumes outcomes are the thing. Rights theory assumes some claims hold whatever the outcome. Contractualism assumes morality is what we could agree to. Those are starting points, and a starting point asserted is not a starting point established.

So a reader is entitled to ask what any of this is tracking. If there are moral facts, what sort of thing are they, and how would a human being ever come to know one? Nothing in the natural world looks like an obligation. You can weigh a pig and measure its cortisol; you cannot find the wrongness in a laboratory. That is the real difficulty, and it is not solved by naming another framework.

The sharpest versionEmotivism puts it most directly: a moral claim does not describe anything, it expresses an attitude. On that view all of the above is elaborate machinery for dressing up what someone already preferred. Pick premises that lead where you were going, argue carefully from them, and present the conclusion as a discovery. That is a serious charge and it applies to this page as much as to anyone making the opposite case.

Two things can be said in reply, and neither is a knockdown. The first is that the charge is symmetrical. If reasoning about ethics is only preference with a suit on, that is just as true of the person defending the farm, and nobody actually lives as though it were: the same people who say morality is only feeling will argue hard that something done to them was unfair, and mean it. The second is that consistency survives the objection. You can show somebody that two things they already believe cannot both be held without ever establishing a single moral fact, and most of the arguments on this site do exactly that.

Which is why the honest position is narrower than it first looks. This page cannot prove that animals matter to a reader who denies every premise it could start from. What it can do is show that the reasons usually given for treating them as not mattering are ones the person giving them does not apply anywhere else.

Emotivism, relativism and the rest, at length

It would be convenient to claim every framework points the same way. Four of the five above do, by different routes, and the fifth, contractualism, has to be widened in ways most people already accept. That convergence is worth something, but it is not the main point.

The main point is that you rarely need to settle the question. Most of the arguments catalogued on this site fail on their own terms: they are inconsistent, or they rest on a claim that is simply false, or they describe what is natural and conclude something about what is right. You can reject them without having decided which theory of ethics is correct.

Browse the argumentsThe reasoning errors involved