Here is how it goes. First, he asks you to imagine having to make a certain sort of choice about your own life. Speaking of ways we might compare the value of different allocations of medical resources, he says:
How can we compare saving a person’s life with, say, making it possible for someone who was confined to bed to return to an active life? We can elicit people’s values on that too. One common method is to describe medical conditions to people — let’s say being a quadriplegic — and tell them that they can choose between 10 years in that condition or some smaller number of years without it. If most would prefer, say, 10 years as a quadriplegic to 4 years of nondisabled life, but would choose 6 years of nondisabled life over 10 with quadriplegia, but have difficulty deciding between 5 years of nondisabled life or 10 years with quadriplegia, then they are, in effect, assessing life with quadriplegia as half as good as nondisabled life.From this this thought-experiment about choices you would make for yourself he draws a conclusion about how we ought to treat other people. He puts it in terms of the specific issue he was just talking about like this:
If that judgment represents a rough average across the population, we might conclude that restoring to nondisabled life two people who would otherwise be quadriplegics is equivalent in value to saving the life of one person, provided the life expectancies of all involved are similar.More generally, the idea seems to be that our social calculations should be based on the idea that one more year of life for a quadriplegic has half the value of one more year for a non-quadriplegic (other things being equal). We should assume that for purposes of distributing medical care, it takes two quadriplegics to equal one healthy non-quadriplegic. Such a system discriminates against the disabled and, for similar reasons, against the old. What is wrong with his reasoning, if anything?
Something about it really bothers me -- not the conclusion, but the reasoning itself -- but I don’t think I have completely figured out what.
One point that is relevant is made by philosopher Tom Regan in another context. Singer's way of thinking reasons from the fact that I can enjoy twice the value that you can enjoy, to the conclusion that in our social calculations my life has twice the value that you have. It views humans as receptacles of value, but does not view them as having value in any other sense. We should respect the value people consume, but not the value that they are. That is how Singer is thinking. On the other hand, if you think that humans have value in and of themselves (if you believe in what Kant called “human dignity”) that gets in the way of sacrificing one person for the sake of another, which is what Singer (as I interpret him) advocates. So you can admit his premise but deny his conclusion.
Another thing that can block the inference that Singer makes is the particular way one might understand the first of these two sorts of value: the value that we consume. If I decide whether I would prefer ten years as a quadriplegic to four years of non-disabled life, I am judging what has the greatest value for me, or to me. Well, what if we all, quadriplegics included, preferred experiencing non-quadriplegic to quadriplegic life at Singer’s fanciful rate of two to one? Couldn’t quadriplegics still consistently deny that other people’s interests should be preferred over theirs at that same rate?
I think it is obvious that they can, though it is not so easy to say exactly why. It seems to have to do, though, with the fact that the two judgements are about profoundly different things. Thoreau would say the first is about expediency, and the second is about right and wrong.