All beings capable of suffering are entitled to the "principle of equal consideration"
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.
I admit that making this distinction can be hard. Human accomplishments and abilities seem to so obviously distinguish us that downplaying our differences might appear to be nothing but a philosophical gambit. But consider: The ultimate problem with giving primary moral consideration to the amazing feats that humans can exclusively accomplish is that doing so requires us to assess all humans in such terms as well. In other words, we would have to undertake different evaluations of suffering for the mentally ill, the infirm, infants, the elderly, those with low IQs, etc. If sentience took a back seat to cognitive ability or skill sets, the moral value of human life would become dependent on variations in intelligence and ability. Needless to say, such a moral code would have horrific consequences.
Let me try to bring this argument down to Earth. Say I’m stranded on an island with a pig. And say the island is stocked with an endless supply of fruits, vegetables, grains, and nuts—enough to feed us both. Am I justified in killing the pig?
The application of equal consideration would require me to consider if the suffering I would cause the pig—indeed, taking its life—was worth satisfying my own taste for pork—something that I hardly need. My answer would have to be no. The pig’s sentience—its status as a non-object capable of suffering—morally trumps my desire to eat a BLT, no matter how much pleasure it gives. No life is worth a sandwich I don’t need.
~ James McWilliams (January 10, 2011)