I should qualify this, but not by much: atheists should be vegans. Most serious issues have some inherent fuzziness involved, and this is no exception. The issue is fairly clear, however, for most of us. While there are some factors worth taking into account, like strict dietary needs, recovery from eating disorders, and surviving in areas where animal farming is necessary, most atheists nonetheless have no good reason to consume factory-farmed animal products.[1. I think there’s good reason to avoid most non-factory farmed animal products, but the issue is more complicated. Since factory farms account for 99% of farmed animals, it’s probably not worth doubling the length of the piece to get the other 1 percent. There’s also a case for limiting consumption to carefully vetted animal products, like oysters, for example, which seem to be ethically okay. Please read references to veganism throughout this piece as reflecting these considerations.] Simply stated, veganism is an ethical no-brainer. Let me channel Peter Singer and suggest that we’d all agree on something like the following moral premise: if we can prevent serious harm without giving up something morally important in return, we ought to prevent that harm. There is of course the large human toll of factory farming—an unsustainable carbon footprint, unbelievable water use, and contribution to antibiotic-resistant bacteria—but a look at what we’re farming is enough to make my point. Factory farming causes extreme, unnecessary harm to animals.[2. I don’t think anyone with even passing familiarity with factory farm practices can deny this, but if you need convincing, the American Society for the Prevention of Cruelty to Animals (ASPCA) has some nice resources to look through.] The benefit we get from animal products over vegan alternatives isn’t important enough to justify the damage that factory farming inflicts on the lives and happiness of conscious creatures. So we ought to prevent the harm caused by factory farming. It’s as simple as that. The case for eating meat is often as crude as pointing to our incisors and laughing about how delicious bacon is, but we live in a world where vegan alternatives are relatively convenient and can provide the nutrients we need with few, if any dietary supplements. Without a need to eat animal products, we can’t eat animal products for defensible moral reasons—as delicious as any steak tastes, the pleasure it gives over and above any vegan or vegetarian alternative is nowhere near the suffering a chicken, cow, or pig undergoes in modern factory farms. There are a few ways around this obvious point, but none are easily available for an atheist. While many believers look to their faith to justify their animal-welfare views, believers can counter this point in ways atheists can’t. Believers can appeal to overriding moral commitments, like the will of God or the word of their holy books (“have dominion over the fish of the sea and over the birds in the heavens,” and so on), and it certainly seems that if an intelligent designer made us, they did it with animal consumption in mind. Atheists, however, don’t have much luck here—though we certainly did evolve to eat meat, a moment’s thought shows that evolution is no guide for good behavior. Atheists could give up the idea that we ought to avoid serious harm unless we have strong moral reasons to do otherwise, but that seems pretty foundational and indispensible to our moral beliefs and reasoning. An atheist can deny moral commitments, full stop, but if we’re going to throw those away to keep eating hamburgers or avoid eating tofu, then our moral compasses are embarrassingly weak. The only other option, then, is to deny that animals can suffer, or suffer in the appropriate ways, or that their suffering matters. Again, believers have more luck here—belief in a soul, as well as the paramount importance most religions put on humanity, provide the only compelling way to make these objections. To start, we know that animals suffer. If we don’t think souls are necessary to explain consciousness, then we can’t treat all animals like Descartes did—as unfeeling meat-machines that only seem as if they experience. Instead, we know that at some point in the branching tree that connected our simplest ancestors to our most recent primate ones, consciousness developed. We can dispute where that line is, but it’s hard to peg that line lower than the animals we farm and eat.[3. As imperfect as it is, a prominent assembly of scientists released a statement called The Cambridge Declaration of Consciousness, which essentially gives the scientific community’s closest consensus view on consciousness. It concludes, “consequently, the weight of evidence indicates that humans are not unique in possessing the neurological substrates that produce consciousness. Non-human animals, including all mammals and birds, and many other creatures, including octopuses, also possess these neurological substrates.”] There are certainly some cognitive skills that are less developed in animals, sometimes greatly so, such as reasoning, memory, a sense of self, and so on. It’s not obvious why this should make animal suffering any less bad and worth preventing. After all, many animals are more developed than human children on certain cognitive tasks, yet we think the suffering of human children matters. We don’t think abusing an infant becomes fine simply because they won’t remember it, or don’t know who they are, or can’t do algebra. It would still be wrong, even if we knew the abuse would cause no lasting damage to the adult person that baby would become. Unless we can point to a relevant difference between infants and animals, other than the arbitrary happenstance that infants share our DNA and cows don’t, we can’t coherently hold that infant suffering is bad while animal suffering isn’t. Insofar as we think suffering should be prevented, we should think all suffering should be prevented. We have nothing but narcissism to justify the unique importance of our taste buds over the suffering of conscious creatures. This leaves us in an uncomfortable place—we know animals can suffer, have no divine reason to suppose that only our suffering matters, and we’re currently inflicting constant and severe suffering to a staggering number of conscious creatures.[4. Without looking, just try to estimate how many farm animals are killed for food every year, and then look at the answer. Take a minute to reflect by how many powers of 10 your estimate was off, and really consider the magnitude of the suffering involved, if you can.] If we’re going to pretend to take morality and rational argument seriously, we can’t ignore the obvious right in front of us. This requires perhaps a radical change in the way we live our lives, and that may very well be demanding on us. It’s a shallow complaint, though, to say that being rational and moral isn’t easy enough. This essay was originally published at Cosmologics, the magazine of the Science, Religion, and Culture program at the Harvard Divinity School. It has been edited for brevity and clarity.