The animistic vision of the ultimate equality of all forms of life is noble, and perhaps ultimately valid, yet it is also one that is impossible for us to live by at this time. There is no remotely objective reason that I know of to privilege the life of person over that of a goldfish or the life of a goldfish over that of a carrot. Theological reasons such as the creation of human beings in the "image of God," still resonate with many people, but for others, myself included, they do not. Appeals to concepts of "sentience" and "consciousness" are secularized forms of the theological reasons. Attempts to define those concepts are hopelessly vague, while attempts to measure them can be dangerously technocratic.

    In the context of the natural world, the individual...