What, if anything, renders all humans morally equal?
In Dale Jamieson (ed.) Peter Singer and his critics, Oxford, 1999, pp. 103–128
Abstract
All humans have an equal basic moral status. They possess the same fundamental rights, and the comparable interests of each person should count the same in calculations that determine social policy. Neither supposed racial differences, nor skin color, sex, sexual orientation, ethnicity, intelligence, nor any other differences among humans negate their fundamental equal worth and dignity. These platitudes are virtually universally affirmed. A white supremacist racist or an admirer of Adolf Hitler who denies them is rightly regarded as beyond the pale of civilized dialogue.2 However, a very simple line of argument developed by Peter Singer challenges our understanding of these platitudes and forces us to rethink the basis and nature of the moral equality of all humans.3 One might try to explain the equal moral status of humans by appeal to our common humanity—all humans are all equally human, after all. But mere species membership is not a sufficient basis for picking out some beings as entitled to greater moral consideration than other beings. If we were to encounter alien beings from another planet, something that looks like green slime but engages in complex behaviors, we would not be justified in failing to extend respectful treatment to the aliens merely on the ground that they belong to another species. If they proved to be like humans in morally relevant respects, then they should be treated the same as humans. Very roughly speaking, if the aliens showed a capacity for rational, autonomous agency, we would be required to include them within the scope of our moral principles. This thought experiment suggests a justification for our current practice of according all and only human beings a special moral status and relegating all nonhuman animals to a lower moral status. There is some intellectual capacity or set of intellectual capacities, call it X, that entitles the possessor of X to treatment as an equal member of the class of persons, to whom special moral principles apply..
