James McWilliams makes his case against meat eating:
We can draw all the distinctions we like between humans and farm animalswe can produce operas, they cannot; we can do calculus, they cannot; we can send smug holiday greeting cards, they cannot. But none of these distinctions undermines the fundamental reality that we're both sentient beings capable of suffering.
If the ethics of eating matter in the least, then our understanding of animals must begin with this premise. Above all else, we must acknowledge that our shared sentience means that humans have a moral responsibility to treat farm animals differently than we treat objects. Specifically, as the philosopher Gary Francione has argued, all beings capable of suffering are entitled to the "principle of equal consideration." What this means is that, before using an animal in any way, we should evaluate what's at stake for everyone involved. We must do so, moreover, on the primary grounds of our shared sentience, thereby downplaying the many differences between humans and farm animals. Just because a farm animal cannot do math or send greeting cards doesn't mean that its capacity for suffering is in any way fundamentally different from our own.