Thought Experiment Number One: The devil comes to you one day and says, "OK, I don't like you, so I'm going to give you the following choice. Either: (A) I will make you miserable for the rest of your natural life, which will be a long and dolorous half century; or: (B) I will make you effortlessly happy for that same duration, plus I will immediately kill five million children whom you don't know in a variety of excruciatingly painful ways. Oh, and since I'm Evil and all, I'm going to do it in front of their parents. Whichever way you choose, you'll forget instantly and completely that I made this offer and that you made this choice. So which do you choose?"
The point of this thought experiment is to point out that personal happiness is not the lone ultimate value, even for a humanist. Besides their need for happiness, people have an equally deep need to live their lives in a manner that they can admire. Notice that this is not merely "higher hedonism" --- i.e., in this thought experiment you do not choose to be good because the thought of being good will make you happier, in a deeper sense, than being selfish. The experiment stipulates that you will immediately forget that you were ever offered this choice. Therefore, there is no hedonic value, on any level, in making the altruistic choice. Yet most people would make the altruistic choice --- or, at least, I like to believe so.
Thought Experiment Number Two: The devil comes to you the next day, not quite satiated with your misery, and says: "OK, yesterday was a wuss question, because you could at least make your decision based on a net gain in happiness over all of humanity. Today, I'm going to offer you the following choice. Either: (A) I will make humanity miserable for the rest of its existence, which will be a long and dolorous million years; or: (B) I will make all of humanity happy for equally long, plus I will permanently bring back slavery, in the ugliest and most racist form that humanity has ever known --- black people will be regarded as subhuman, and forced to grow up in complete degradation and servitude to white people --- except, of course, that I've made everybody happy, so the slaves too will be joyful in their subjection, as they weren't in the past. As before, nobody will know that this choice was made. Now choose."
The point of this thought experiment is that even global happiness is not the ultimate value. There are things that we value --- like "justice" --- more than happiness. Or, at least, happiness alone cannot compensate for the loss of all other values.
Thought Experiment Number Three: Thoroughly pleased with itself, the devil comes to your doorstep a third time. "OK, that was fun at first, but now it's getting boring. When everybody's miserable, there's no point in being Evil. I'm going to roll back that whole universal misery till the end of time thing. But since we're such friends, I've got another present for you. I'm going to kill your son. No, you don't get a choice. Here's your choice. Either: (A) you'll immediately forget he ever existed, and therefore feel no grief whatsoever; or: (B) you'll remember him always, and miss him every day of the rest of your life, just like any other parent. Either way, you'll forget this decision. What do you say?"
The point of this experiment is that the result of the previous two experiments are not just artifacts of absurdly extreme situations. Even given the choice, many people would choose misery over happiness in their own personal lives.
All this was prompted by recent musings on why one might choose to be unhappy rather than let go of something precious. I wondered: is it necessarily irrational? No, not necessarily. You have to weigh your happiness against whatever you must give up to attain it.
p.s. Yes, all of the above scenarios are arguably related to the various Matrix dilemmas described by James Pryor, although I think deception plays less central a role in these thought experiments than in Pryor's. If you take this line of thought a little farther, you might conclude that you wouldn't want to live in heaven either.