This article found on www.getpocket.com describes the philosophy and wisdom of Christine Korsgaard, a distinguished philosopher who has taught at Harvard for most of her career.
What We Owe a Rabbit: Considering the contrast between the values of human and animal lives, according to which killing a human is wrong in a way that killing an animal is not.Christine Korsgaard
Since the publication of Peter Singer’s Animal Liberation in 1975, there has been a notable increase in vegetarianism or veganism as a personal choice by individuals, and in the protection of animals from cruel treatment in factory farms and scientific research, both through law and through public pressure on businesses and institutions. Yet most people are not vegetarians: approximately 9.5 billion animals die annually in food production in the United States, and the carnivores who think about it tend to console themselves with the belief that the cruelties of factory farming are being ameliorated, and that if this is done, there is nothing wrong with killing animals painlessly for food. Korsgaard firmly rejects this outlook, not just because it ignores the scale of suffering still imposed on farmed animals, but because it depends on a false contrast between the values of human and animal lives, according to which killing a human is wrong in a way that killing an animal is not.
For even if the rabbit’s life is not as important to her as yours is to you, nevertheless, for her it contains absolutely everything of value, all that can ever be good or bad for her, except possibly the lives of her offspring. The end of her life is the end of all value and goodness for her. So there is something imponderable about these comparisons.Christine Korsgaard
So the lives of humans and of other animals are very different. But does that mean that human lives are more important or more valuable than the lives of animals? Korsgaard asks, in keeping with her skepticism about untethered absolute value, “More important or valuable to whom?” Your life is more valuable to you than it is to a rabbit, but the rabbit’s life is more valuable to the rabbit than it is to you. And if you protest that the rabbit’s life is not as important to the rabbit as your life is to you, Korsgaard’s response is that even though you have a conception of your life as a whole that the rabbit lacks, this does not show that your life is more valuable:
Korsgaard denies that the human capacity to appreciate literature, music, and science makes human lives more valuable. She observes that in comparing humans with one another, most of us do not think that one individual is more valuable simply because more good things happen in his or her life, and she holds that we should take the same view when comparing humans with other animals. There are just different individuals, and the life of each of them is of ultimate value to the creature itself.