Where do vegans draw the line?

The objection

“If avoiding harm to animals is the principle, where does it end? Insects, plankton, bacteria, the microbes you kill washing your hands? Either you draw an arbitrary line, exposing the whole project as inconsistent, or you follow it to absurdity and can’t live at all.”

The answer

The dilemma assumes that any line has to be either arbitrary or impossible to live by. A line fixed by what a creature can feel is neither, and the evidence now says a good deal about where it falls.

Where do vegans draw the line?

Vegans draw the line at sentience, the capacity to have experiences and above all to suffer, which takes in cows, pigs, chickens and fish and leaves out plants and bacteria. Jeremy Bentham put the test as a question in 1789: “Can they suffer?” [5]. The New York Declaration on Animal Consciousness, issued at New York University in 2024 and signed by 613 people by October 2026, finds strong scientific support for conscious experience in mammals and birds, and at least a realistic possibility of it in all vertebrates, fish included, and in many invertebrates, among them octopuses, crabs, lobsters and insects [2]. In 2021 a review for the UK government, led by Jonathan Birch of the London School of Economics, weighed over 300 studies and recommended that all cephalopod molluscs, such as octopuses, and all decapod crustaceans, such as crabs and lobsters, be regarded as sentient [1][3]. Grading the evidence group by group, the review’s five authors found strong evidence of sentience in true crabs and substantial evidence in lobsters and crayfish (Crump et al. 2022) [7], and strong evidence in octopuses (Schnell et al. 2026) [8]. The UK’s Animal Welfare (Sentience) Act 2022 followed the review’s advice and counts octopuses, crabs and lobsters as animals alongside vertebrates [3][4], though all the Act does with that definition is set up a committee to report on whether government policy pays all due regard to the welfare of animals as sentient beings [4].

Are insects and bacteria inside the line?

Insects may well be, and bacteria show no sign of it. The 2024 declaration names insects among the animals with a realistic possibility of conscious experience [2], and the evidence is set out in whether insects feel pain. In 2019 Lincoln Taiz and seven co-authors set out a hypothesis from Feinberg and Mallatt, based on a survey of brain anatomy and behaviour across a broad range of animals, under which the only animals meeting the criteria for consciousness were vertebrates, fish included, arthropods such as insects and crabs, and cephalopods such as octopuses [6]. In light of that analysis they judged the chance that plants are conscious “effectively nil”, since plants have no neurons or brain [6], and a bacterium is a single cell with no neurons at all. Plants have their own answer, and so do oysters and mussels, which the declaration does not name and which make a harder case.

Does a blurry edge make the line arbitrary?

A blurry edge doesn’t make a line arbitrary, and we accept blurry edges everywhere else. Nobody can name the second at which twilight becomes night, yet midnight is plainly dark, and there is no exact age at which a child becomes an adult, yet we still protect children. Uncertainty about a mosquito casts no doubt on a pig. The alternative on offer, that if you can’t protect everything perfectly you may as well protect nothing, is one we reject at once for people: being unable to save every human doesn’t free you to harm the one in front of you. For the cases at the edge, the 2024 declaration’s answer is caution, since where conscious experience is a realistic possibility “it is irresponsible to ignore that possibility in decisions affecting that animal” [2].