Some people argue that veganism is an overreach of anthropomorphism — that vegans wrongly project human emotions, feelings, and ‘souls’ onto animals, and that’s the reason why vegans worry about harming them.
On the other hand, I’ve also found that very few people completely agree with Descartes’ assessment that (non-human) animals are merely unconscious, mindless organic automata who are incapable of suffering or emotion. Most people who have had close contact with a companion animal can attest that they can seem genuinely distraught or genuinely happy in certain situations. But we don’t have to rely on anecdotal evidence — there’s more and more scientific research supporting the idea that many animals likely have some sort of conscious experience.
However, to me, this whole question is really just setting up a straw man argument.
Sure, let’s go ahead and assume that animals don’t have a conscious experience that is similar to humans’ in any way, shape, or form. They may indeed be little Cartesian automata, who just bumble through the world reacting to stimuli and never experience happiness, fear, or pain.
But what I do know is that when a dog comes over to me, I can: (1) give it some pats, and it will roll over to expose its belly for a thorough scratching, or I can (2) hit it with a stick, and it will yelp, cower, and run away, or I can (3) kill it, and bye-bye doggo. Regardless of our current scientific understanding of that animal’s inner workings, I would choose to pet the animal rather than to cause unnecessary harm to it.
When most of us see a nest of robins outside our window, or a giraffe roaming the savannah, we want to let these creatures be, rather than hurt or kill them. I don’t want to cause unnecessary death and injury to other life forms for no good reason, regardless of whether these life forms have human-style consciousness or not.