Debate: Should The Non-Aggression Principle Apply to Animals?

by Michael Huemer

This article is part of our special print debate issue. Below, you’ll find the case in favor of the resolution, followed by the case against the motion.

Yes, it should!

By Michael Huemer

The Non-Aggression Presumption

Nearly everyone agrees with the general rule that one should not initiate force against other people or their property (otherwise known as “aggressing” against them) without their consent. Some libertarians hold this as an absolute prohibition, such that it is never permissible to commit aggression, regardless of the consequences. If a single, minor act of aggression would save a billion lives, these libertarians would say it would still be wrong to commit the aggression.

I view the absolutist position as indefensible, not simply because of what it says about the above (extremely unlikely) hypothetical, but because of what it implies about risk-imposition. I think the absolutist position implies that it would also be absolutely impermissible to initiate any risk of physical harm to others without their consent. (If this is permissible, consider that a sufficient number of such actions entails an arbitrarily high probability of harm.) I also believe that essentially every action entails some nonzero risk of causing essentially any physically possible outcome, including physical harm to others. Thus, I think the absolutist is committed to the view that all actions (or all positive actions) are impermissible, and thus that everyone is immediately morally required to remain completely passive, not even breathing, until they die.

Rather than an absolute prohibition, therefore, I advocate a presumption against aggression: it is wrong to initiate force against other people or their property without a good reason. I suggest that we rely on common sense moral intuitions to identify what are and are not sufficient reasons for coercion. This turns out to be sufficient to justify libertarian political conclusions, given ethical intuitions shared by almost everyone, regardless of political affiliation. I have discussed the above points at length elsewhere, so I will not elaborate on them further but will take them for granted here.

The Question of Non-human Animals

What about other (non-human) animals? Human beings frequently commit extreme aggression against them for trivial reasons. For instance, some people go out into nature and kill other animals purely for entertainment. Almost everyone eats body parts of other animals for pleasure on a regular basis, knowing that these products are provided through extreme acts of aggression. Our attitudes about these things are strikingly different from our attitudes toward the analogous behaviors directed at members of our own species. Those who kill us purely for pleasure are psychopathic murderers, the most horrifyingly evil class of criminals.

Does the non-aggression principle apply to non-human animals? Given what we have said above, the question is whether there is a moral presumption against aggressing against other animals. That is, is it wrong to commit such aggression without a good reason?

Why Not Aggress?

We might start by asking why it is wrong to aggress against people. The answer seems to have something to do with the fact that aggression is generally harmful, that harms are generally bad, and that one generally ought not to do bad things for no reason. On the face of it, all of this is equally true of aggression against other animals. Granted, there are many ways in which humans differ from other animals, but the fact that being physically attacked harms us is not among them. Is there some reason why harms to us are bad yet harms to other animals are not bad?

What’s the Difference?

Moral facts depend upon descriptive facts: if there is a moral difference between two entities, then there must be some descriptive, factual difference that explains why there is that moral difference. (This is among the very few uncontroversial principles in ethics.) Thus, if it is bad to harm humans but not bad to harm other animals, then there must be some descriptive, factual difference between humans and animals that explains this. What might this difference be?

Here are some answers I have heard:

Humans are more intelligent than animals. This somehow means that their suffering doesn’t matter, and therefore, it is morally alright to aggress against them for no reason.

Reply: Some severely mentally disabled humans are less intelligent than some animals. So the above view implies that it would also be fine to attack these people for no particular reason. We could similarly attack infants for fun.

Only humans are part of society.

Reply: This implies that we could attack hermits for fun and, again, babies.

Only humans can understand morality.

Reply: This implies that we could aggress against children, psychopaths, and other people who don’t understand morality.

Rights reply responsibilities. Animals have no moral responsibilities; therefore, they have no rights.

Reply: Again, this implies that we could aggress against babies and the severely mentally disabled.

Humans have souls.

Reply: (a) It is controversial whether anyone has a soul. If we don’t have them, will it be fine to attack us for no reason? (b) The evidence for humans having souls – that we have consciousness – also applies to other animals. If we need a soul to have conscious mental states, then so do the other animals. If we don’t, then they don’t. Are there any morally relevant differences between humans and animals? Due to their greater intelligence, normal, adult human beings have some interests that animals lack, such as an interest in planning their lives, or an interest in education. The lives of human beings are also typically more valuable than those of animals; hence, if you must choose between saving a child and saving a dog, you should save the child. But none of this makes it alright to attack other animals for no reason or for trivial reasons, such as for entertainment or pleasure.

No, it shouldn’t!

By Felipe Diego Gomides


When reflecting on the relationship between normative philosophy and animals, more often than not, one of two things is emphasized. Some focus on the moral importance of suffering and show images of brutish, cruel treatment of animals. Others focus on the nature of animals, discussing consciousness, biology, and cases where animals are compared to impaired or not fully developed humans. Comparing children to dolphins and criticizing food production can be interesting issues. However, our focus in this essay is on the scope and application of a specific principle: the Non-Aggression Principle (NAP). The NAP is the moral principle that rejects the initiation of force. 

Even if the NAP does not apply to animals, as I will argue, those convinced that animals have claims to our consideration can profit by understanding how the NAP relates to their position. To accomplish this goal I will take the following steps. First, I will specify which version of the NAP I will explore: Ayn Rand’s non-initiation of force principle (NIOFP). Second, I will explain what it is, its place within Objectivist ethics, what the requirements for its application are, and how animals fit into that picture. Third and finally, I will deal with one main objection to the position by explaining how an egoistic view of morality can reject cruelty to animals. The upshot is that humans will be able to relate to animals by not inflicting unnecessary suffering, without attributing them moral agency or rights. 

When presenting the NAP, Matt Zwolinski (2016) and Walter Block (2008) identify Rand as one of its important defenders, while Daryl Wright thinks that connection is questionable. Adam Mossoff and Fred Miller suggest that the NIOFP is a version of the NAP. To cut through this debate, I will make explicit what distinguishes the NIOFP from other versions of the NAP. Block usefully points out the existence of a Rothbardian version of the principle and a Randian version of the principle, singling out differences on the means of justification. For Block (2018), Rothbard holds that the initiation of force violates an axiomatic principle of self-ownership, while Rand thinks that it impedes one’s independence. Zwolinski adds a third version, which he calls the “commonsense moral principle” of taking the NAP to be a simple, intuitive, non-moralized foundation for a complex political philosophy.

Rand’s version is an application of other moral concepts to the problem of social interaction. It is neither an axiom nor intuition; it is a mid-level principle in a long line of reasoning. Choosing the NIOFP has the advantage of honoring the needs of human nature without appealing to vague intuitions or positing self-ownership as an axiom. 

The formulation of the NIOFP that best encapsulates Rand’s thinking on it is: “The basic political principle of the Objectivist ethics is: no man may initiate the use of physical force against others.” She then adds that this ban applies equally to every man, government, and group; that force may be used only in retaliation against those who initiate it; and that the use of force is not a rational means to achieve value. When discussing the nature of government, Rand further adds that the sole way to violate rights is by initiating force. 

To understand the place of the NIOFP within Rand’s ethics, we need to understand that, for her, morality is composed of normative principles of how living, volitionally conscious creatures—humans—achieve flourishing. Politics is morality applied to the issue of how humans can live together. Political principles are moral, but they are developed from one specific moral principle: the NIOFP. That’s why Rand calls it a “basic political principle.” It is a first application of an important moral consideration: the relationship between force and human life.

Rand identifies three options for survival: imitation, predation, and production. Some non-human animals survive solely by using force, by preying on other creatures. Humans could try imitating others, but we will die if those others don’t know what they’re doing. What makes humans’ method of survival different is that we need to freely use our mind to understand the world and reshape it to suit our needs. Objectivist morality holds that trying to live by force undermines living by one’s own judgment, which leads to perishing. This leaves production as the proper means of human survival.

Because we survive through production, living together can be good. It is production that allows for trading, and a society based on trade is the proper environment for human flourishing. Force is the opposite of trading. When force enters the public square, trading goes out of it. Banning the initiation of force allows us to relate to each other mutually as producers. The NIOF protects the relationship between two beings who are able to enter into social relationships and renounce the initiation of force, beings able to respect each other as producers and relate to each other as such. Non-human animals can’t do any of this.

Humans are able to change their environment and build on their present efforts because they have a conceptual faculty. Non-human animals cannot exert intentional, long-range control over their environment. We need to direct our life as a whole with our minds to keep living because we have no automatic knowledge for doing this. That’s why we need moral and political principles—and why non-human animals don’t. 

A thoughtful objection to the NIOFP could be: “If an animal is not protected by this version of the NAP, does that imply that cruelty toward animals is permissible?”

This does not follow. On Rand’s view, although non-human animals have no ethics, they are valuing creatures. Since they are mortal, there are things that are good and bad for them, which counts for their well-being. In “The Ethics of Emergencies,” Rand urges us to recognize our “common bond among living beings.” Because “life is the source of all values,” it is important to take into consideration the potential value all life can offer us. 

We can learn about the nature of things by observing animals—from producing honey to aerodynamics. Biology can further the knowledge of our nature. The relationship with a pet, watching birds, butterflies, and even cat videos are significant sources of pleasure. There are inexhaustible amounts of value that animals open to us. Inflicting gratuitous suffering on animals is a conscious choice that fails to recognize that they are living beings. 

Cruelty should have consequences: social and market consequences, not political ones. Cruelty to animals should be solved with innovation and competition. If companies can create better nutritious meat through cruelty-free processes, it should be sold and praised as a value, not as a duty through guilt-inducing rhetoric. 

The motivation behind caring about animals should be pro-human. Putting humans first is putting reason first, and putting reason first is putting down cruelty.

Michael Huemer is a professor of philosophy at the University of Colorado Boulder, known for his work in epistemology, ethics, metaphysics, and political philosophy. He is a leading proponent of ethical intuitionism and phenomenal conservatism, offering original arguments for moral realism and justified belief. In The Problem of Political Authority, he challenges the legitimacy of government coercion and defends philosophical anarchism. Huemer is also an advocate of ethical vegetarianism and has written extensively on animal ethics and the nature of moral responsibility.

F. D. M. Gomides is a corporate philosopher responsible for founding the quality system of a startup valued over 1 million USD. He has managed both the Prometheus Fellowship and New Frontiers of Objectivism for Students For Liberty, and has founded study groups on issues ranging from libertarian political philosophy to contemporary ethics. He works as a consultant on corporate culture and training and is also chief editor of Objetivismo Brasil.

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