Notes from Around the Sundial

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Gnomon's column image, showing a sundial surrounded with the words Notes From Around the Sundial'

And I think to myself, what a wonderful world!

The Philosophy of Identity

This week I thought I'd dabble in some philosophy. I'm not going to present any answers, just some questions, to get you thinking. If you like thinking about things like this, you might like to read the book 'Sophie's World' by Jostein Gaarder, which is a good introduction to all the basic principles of Philosophy.

The story of George Washington chopping down a cherry tree is trite, uninteresting and discredited, but the story of his axe leads to an interesting problem in philosophy: the question of 'identity'. A similar theme is explored in the story of Locke's Socks, while the Ship of Theseus, the ancient Greek hero, explores the issue further.

Washington and the Cherry Tree

American children are all told the story of George Washington and the cherry tree. The young Washington is supposed to have taken his father's axe one day and chopped down a cherry tree. When his father returned home and found the destruction, he asked his son had he done it. 'Father, I cannot tell a lie', replied George, and admitted to the deed. The intention of the story is to show that high moral values will lead you to a good career. Of course, the actual effect is probably the opposite: if a child as stupid as that can get to be President, maybe I could too!

The story is more than likely not true, but that's not important to our investigation. What is important is what happened afterwards. An old guy living near George Washington's birthplace remarks jocularly, that he owns the very axe which Washington used to chop down the tree. The head has been changed twice and the handle three times, but it is still the same axe!

We laugh at this joke, but are puzzled by it at the same time. Does changing the handle of an axe change it into a different axe, or is it still George Washington's axe? The same question can be asked about changing the head. This sort of thing goes on all the time. You cross a river every day on your way to work, and it is the same river although the water in it has flowed on and been replaced by different water. You yourself are composed of cells which die and are replaced by other cells, but you are still the same you.

Locke's Socks

The problem was studied by the philosopher, Locke. He mused on the fact that his socks develop holes and he darns them, but they are still his socks. Eventually the entire socks could be replaced and they would still be his socks - this doesn't just mean that they belong to him, but that they are the same socks.

The Ship of Theseus

The ship of Theseus is a fictional story intended to explore this further.

Theseus is an ancient Greek hero who likes to sail around in his ship. The ship is old, and a piece of it falls off into the sea and floats away. When Theseus returns to port, he replaces the piece, and continues to sail in his ship, which is still the same ship. The next day, another piece falls off, and that evening Theseus replaces it. This continues, and eventually the entire ship has been replaced with new wood, but it is still the ship of Theseus.

Meanwhile, due to the strange currents in the Aegean Sea, all the pieces of his ship which fell into the sea have been carried away and washed up on a particular beach where another Greek, lets call him Aristotle, assembles them into a ship. This 'new' ship is composed of all the parts of the original ship of Theseus, so it is in fact the Ship of Theseus, although it now belongs to Aristotle. So now we have two copies of the ship, and they are both the original ship.

So how do we reconcile this apparent paradox? Is it meaningless to say that anything is anything? A ship is a useful concept - should we say that changing one atom of the ship stops it being the same ship? Are you a different person every time a cell dies or you see something that changes the arrangement of memories in your brain? Is there such a thing as identity at all?

As I said at the start, I'm not providing you with any answers here, but I hope that I've got you thinking. If you know the answers, by all means let me know.

Notes from Around the Sundial Archive


05.03.09 Front Page

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