Let me describe to you my dream piece of philosophy.

It’s not too long. Ideally fewer than three pages, though up to five is okay as long as every word is necessary. The title is something I read quickly, then read again more slowly. It makes me say ‘What’s all this about then?’ under my breath. The piece itself is technical but not tedious. The implications are wide but the focus is tight.

There’s a nice juicy example. It’s got a sense of danger to it and an element of suspense. It reads almost like a detective story. By the time it’s over the point of the example is obvious, but the implications are spelt out anyway. This is done with a kind of quiet swagger, detectable only through a few italicised words.

And it’s a slam dunk. There are no possible ifs and no possible buts, no assumptions undefended or questions unanswered. It’s not so much a line in the sand as a crack in the earth. You can’t ignore it or undermine it. Your only choice, should you encounter it, is to work around it.

So far, I've only found two pieces like this. This is one of them.

A bit of context before we begin. This extract is from Derek Parfit’s Reasons and Persons. Up to this point, he’s been discussing the self-interest theory of rationality, abbreviated as S. This is the theory which claims that a person is acting rationally if and only if they are acting in their own self-interest (and their self-interest is that their own life go as well as possible). Now it seems to follow from this theory that rational persons should be disposed to be never self-denying. That is, they should never knowingly do what is worse for them. Every decision they make should be for their own benefit.

However, most people recognise that being so selfish is a bad way of making your life go well. People who care about nothing but their own happiness run up against what is called the paradox of hedonism (it’s not really a paradox, but the name has stuck): the harder you try to be happy, the more difficult it is. William Bennett said it nicely:

“Happiness is like a cat, If you try to coax it or call it, it will avoid you; it will never come. But if you pay no attention to it and go about your business, you'll find it rubbing against your legs and jumping into your lap.”

You make your life go better in the long-run if you’re disposed to be sometimes self-denying. Sometimes doing things that are worse for you is the best way of achieving the aim of the self-interest theory of rationality: making your life go as well as possible. The problem is that this disposition is irrational on the very same theory! The self-interest theory tells you that it’s rational to give yourself a disposition that it judges to be irrational.

Contradiction! Or so it seems...


"I turn now to a new question. A theory may be unacceptable even though it does not fail in its own terms. It is true of many people that it would be worse for them if they were never self-denying. Does this give us independent grounds to reject S?

According to S, it would be rational for each of these people to cause himself to have, or to keep, one of the best possible sets of motives, in self-interested terms. Which these sets are is, in part, a factual question. And the details of the answer would be different for different people in different circumstances. But we know the following, about each of these people. Since it would be worse for him if he was never self-denying, it would be better for him if he was sometimes self-denying. It would be better for him if he was sometimes disposed to do what he believes will be worse for him. S claims that acting in this way is irrational. If such a person believes S, it tells him to cause himself to be disposed to act in a way that S claims to be irrational. Is this a damaging implication? Does it give us any reason to reject S?

Consider Schelling's Answer To Armed Robbery.

A man breaks into my house. He hears me calling the police. But, since the nearest town is far away, the police cannot arrive in less than fifteen minutes. The man orders me to open the safe in which I hoard my gold. He threatens that, unless he gets the gold in the next five minutes, he will start shooting my children, one by one.

What is it rational for me to do? I need the answer fast. I realise that it would not be rational to give this man the gold. The man knows that, if he simply takes the gold, either I or my children could tell the police the make and number of the car in which he drives away. So there is a great risk that, if he gets the gold, he will kill me and my children before he drives away.

Since it would be irrational to give this man the gold, should I ignore his threat? This would also be irrational. There is a great risk that he will kill one of my children, to make me believe his threat that, unless he gets the gold, he will kill my other children.

What should I do? It is very likely that, whether or not I give this man the gold, he will kill us all. I am in a desperate position. Fortunately, I remember reading Schelling's The Strategy of Conflict. I also have a special drug, conveniently at hand. This drug causes one to be, for a brief period, very irrational. Before the man can stop me, I reach for the bottle and drink. Within a few seconds, it becomes apparent that I am crazy. Reeling about the room, I say to the man: ‘Go ahead. I love my children. So please kill them.’ The man tries to get the gold by torturing me. I cry out: ‘This is agony. So please go on.’

Given the state that I am in, the man is now powerless. He can do nothing that will induce me to open the safe. Threats and torture cannot force concessions from someone who is so irrational. The man can only flee, hoping to escape the police. And, since I am in this state, he is less likely to believe that I would record the number of his car. He therefore has less reason to kill me.

While I am in this state, I shall act in irrational ways. There is a risk that, before the police arrive, I may harm myself or my children. But, since I have no gun, this risk is small. And making myself irrational is the best way to reduce the great risk that this man will kill us all.

On any plausible theory about rationality, it would be rational for me, in this case, to cause myself to become for a period irrational. This answers the question that I asked above. S might tell us to cause ourselves to be disposed to act in ways that S claims to be irrational. This is no objection to S. As the case just given shows, an acceptable theory about rationality can tell us to cause ourselves to do what, in its own terms, is irrational... Since it was rational for me to cause myself to be like this, this is a case of rational irrationality."

It can be rational to cause yourself to act irrationally! It can be rational to cause yourself to act irrationally! Spray-paint it on busses and shout it from the rooftops! It can be rational to cause yourself to act irrationally! Tell every man, woman and child, with joy in your heart and foam in your mouth!

As nutty as this example is, the important wider point is that the self-interest theory of rationality is not self-defeating. What Parfit has given us is a kind of blueprint for what self-interested persons should do to make their lives go as well as possible: namely, stop wanting their lives to go as well as possible. Only by wanting something else can you get what you originally wanted.

There’s a kind of pleasing cosmic justice in this set-up: people with selfish dispositions are thwarted by their own selfishness, whilst people with self-denying dispositions live good lives without really trying. That’s how it’s supposed to go down at least. Whether or not that happens in reality is an open question.

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