Where do you draw the line, insects, bacteria?

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

This is meant to corner you between arbitrariness and absurdity. The line, though, is neither arbitrary nor invisible. It is sentience: the capacity to have subjective experiences, above all the capacity to suffer. This is the criterion Bentham reached for centuries ago, and the point where modern science has converged. A government-commissioned LSE review weighed over 300 studies and concluded that even crabs, lobsters and octopuses are very likely sentient [1], and the 2024 New York Declaration on Animal Consciousness, signed by hundreds of researchers, holds there is at least a realistic possibility of conscious experience across all vertebrates and many invertebrates [2]. A cow, a pig, a chicken, a fish are not borderline cases. They sit squarely inside the line.

Here is where the objection cheats. Hard cases at the edge don’t erase the easy cases at the centre. We can’t name the exact second twilight becomes night, yet no one doubts that midnight is dark. We can’t fix the precise age of adulthood, yet we still protect children. Vagueness at a boundary is never a licence to act as though the boundary doesn’t exist. The honest response is to protect confidently where sentience is clear, give the benefit of the doubt where it’s plausible, and not pretend that uncertainty about a bacterium tells us anything about a pig.

The alternative on offer is that if you can’t protect everything perfectly you may as well protect nothing. That’s nihilism wearing rigour’s clothes, and we reject it instantly everywhere else. The fact that you can’t save every human doesn’t free you to harm the one in front of you.

The useful question was never “where exactly is the line?” It is whether your uncertainty about the insect can excuse what you choose to do to the chicken, when farmed animals are plainly able to suffer.