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Four philosophical questions to make your brain hurt

Jean-Paul Sartre (right)
Gauloise. Check. Expansive hand gestures. Check. Get that philosopher look

David Bain
It's World Philosophy Day - an opportunity to contemplate one's very existence and whether computer monitors really exist, says David Bain.

People expect different things of philosophers. Some expect us to be sages. When these people meet me, my heart sinks, since I know theirs is about to. Others expect us to have a steady supply of aphorisms up our sleeves, such as that love is never having to say you're sorry (something no partner of mine has ever been persuaded of).

They too are disappointed when they meet me, especially when I say that the glass so beloved by optimists and pessimists is both half full and half empty.

Others expect of us not sagacity, but madness, or at least outlandish beliefs. And here, it must be said, some philosophers really have delivered. Thales believed that everything is made of water, for example, while Pythagoras avoided eating beans because he believed they have souls.

Andre Glucksmann, Bernard-Henri Levy
Eccentric hair: The mark of a modern-day French philosopher

As Princeton philosopher David Lewis once said: "When philosophers follow where argument leads, too often they are led to doctrines indistinguishable from sheer lunacy."

But beware. this is the same David Lewis who believed that, for each of the ways things might have been but are not, there is a world at which they are that way, eg a world at which your counterpart is spending today with the world's greatest sex god or goddess.

And, reassuring though it can be to think that at least that counterpart is having fun, even those impressed with Lewis's towering intellect have often found these other worlds of his hard to swallow.

Not all philosophers pin such striking colours to the mast, but there is a good reason why people associate the subject with surprising views. Philosophy involves standing back and thinking - intensely and rigorously - about aspects of our lives that are at once ordinary and fundamental.

And when the surface is scratched, what you find below is extraordinary - or, rather, extraordinarily difficult to make good, clear sense of. Lying in wait are arguments that lead to, if not sheer lunacy, then bullets we're loathe to bite.

So, with World Philosophy Day upon us, here are some pesky arguments to apply your minds to:

1. SHOULD WE KILL HEALTHY PEOPLE FOR THEIR ORGANS?

Suppose Bill is a healthy man without family or loved ones. Would it be ok painlessly to kill him if his organs would save five people, one of whom needs a heart, another a kidney, and so on? If not, why not?

Consider another case: you and six others are kidnapped, and the kidnapper somehow persuades you that if you shoot dead one of the other hostages, he will set the remaining five free, whereas if you do not, he will shoot all six. (Either way, he'll release you.)

If in this case you should kill one to save five, why not in the previous, organs case? If in this case too you have qualms, consider yet another: you're in the cab of a runaway tram and see five people tied to the track ahead. You have the option of sending the tram on to the track forking off to the left, on which only one person is tied. Surely you should send the tram left, killing one to save five.

But then why not kill Bill?

2. ARE YOU THE SAME PERSON WHO STARTED READING THIS ARTICLE?

Consider a photo of someone you think is you eight years ago. What makes that person you? You might say he she was composed of the same cells as you now. But most of your cells are replaced every seven years. You might instead say you're an organism, a particular human being, and that organisms can survive cell replacement - this oak being the same tree as the sapling I planted last year.

But are you really an entire human being? If surgeons swapped George Bush's brain for yours, surely the Bush look-alike, recovering from the operation in the White House, would be you. Hence it is tempting to say that you are a human brain, not a human being.

But why the brain and not the spleen? Presumably because the brain supports your mental states, eg your hopes, fears, beliefs, values, and memories. But then it looks like it's actually those mental states that count, not the brain supporting them. So the view is that even if the surgeons didn't implant your brain in Bush's skull, but merely scanned it, wiped it, and then imprinted its states on to Bush's pre-wiped brain, the Bush look-alike recovering in the White House would again be you.

But the view faces a problem: what if surgeons imprinted your mental states on two pre-wiped brains: George Bush's and Gordon Brown's? Would you be in the White House or in Downing Street? There's nothing on which to base a sensible choice. Yet one person cannot be in two places at once.

In the end, then, no attempt to make sense of your continued existence over time works. You are not the person who started reading this article.

3. IS THAT REALLY A COMPUTER SCREEN IN FRONT OF YOU?

What reason do you have to believe there's a computer screen in front of you? Presumably that you see it, or seem to. But our senses occasionally mislead us. A straight stick half-submerged in water sometimes look bent; two equally long lines sometimes look different lengths.

Muller-Lyer illusion
Are things always as they seem? The Muller-Lyer illusion indicates not

But this, you might reply, doesn't show that the senses cannot provide good reasons for beliefs about the world. By analogy, even an imperfect barometer can give you good reason to believe it's about to rain.

Before relying on the barometer, after all, you might independently check it by going outside to see whether it tends to rain when the barometer indicates that it will. You establish that the barometer is right 99% of the time. After that, surely, its readings can be good reasons to believe it will rain.

Perhaps so, but the analogy fails. For you cannot independently check your senses. You cannot jump outside of the experiences they provide to check they're generally reliable. So your senses give you no reason at all to believe that there is a computer screen in front of you."

4. DID YOU REALLY CHOOSE TO READ THIS ARTICLE?

Suppose that Fred existed shortly after the Big Bang. He had unlimited intelligence and memory, and knew all the scientific laws governing the universe and all the properties of every particle that then existed. Thus equipped, billions of years ago, he could have worked out that, eventually, planet Earth would come to exist, that you would too, and that right now you would be reading this article.

After all, even back then he could have worked out all the facts about the location and state of every particle that now exists.

And once those facts are fixed, so is the fact that you are now reading this article. No one's denying you chose to read this. But your choice had causes (certain events in your brain, for example), which in turn had causes, and so on right back to the Big Bang. So your reading this was predictable by Fred long before you existed. Once you came along, it was already far too late for you to do anything about it.

Now, of course, Fred didn't really exist, so he didn't really predict your every move. But the point is: he could have. You might object that modern physics tells us that there is a certain amount of fundamental randomness in the universe, and that this would have upset Fred's predictions. But is this reassuring? Notice that, in ordinary life, it is precisely when people act unpredictably that we sometimes question whether they have acted freely and responsibly. So freewill begins to look incompatible both with causal determination and with randomness. None of us, then, ever do anything freely and responsibly."

IN CONCLUSION

Let me be clear: the point is absolutely not that you or I must bite these bullets. Some philosophers have a taste for bullets; but few would accept all the conclusions above and many would accept none. But the point, when you reject a conclusion, is to diagnose where the argument for it goes wrong.

Doing this in philosophy goes hand-in-hand with the constructive side of our subject, with providing sane, rigorous, and illuminating accounts of central aspects of our existence: freewill, morality, justice, beauty, consciousness, knowledge, truth, meaning, and so on.

Rarely does this allow us to put everything back where we found it. There are some surprises, some bullets that have to be bitten; sometimes it's a matter simply of deciding which. But even when our commonsense conceptions survive more or less intact, understanding is deepened. As TS Eliot once wrote:

"…the end of our exploring,

Will be to arrive where we started,

And know the place for the first time."

David Bain is a lecturer in philosophy at the University of Glasgow

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