mind & identity · new to this edition

twin earth

a planet exactly like ours, except that the stuff in its rivers is not water. hilary putnam used it to argue that what you mean is not settled by anything inside your head. the bill for that conclusion arrives later.

after Hilary Putnam, Tyler Burge, Jerry Fodor, Paul Boghossian, John Searle · about 5 minutes

In 1975 the American philosopher Hilary Putnam published a long essay called “The Meaning of ‘Meaning’”. Its most famous passage asks you to picture a second Earth, identical to ours down to the last person, with one difference in what fills its seas. From that single change Putnam drew a conclusion he put bluntly: “meanings” just ain’t in the head. Answer each step before reading on. The first step asks about a glass of liquid; the last asks whether you know what you are thinking.

is the stuff in the glass water?

Your ship lands on a planet that looks exactly like Earth. It has the same continents, the same cities and a double of every person you know, all speaking what they call English. Rain falls, rivers run to the sea, and taps run clear.

Your chemists take a sample. The liquid looks, tastes and quenches thirst exactly as water does, but it is not H₂O. It has a long and quite different chemical formula, which they abbreviate as XYZ. There is no H₂O anywhere on the planet.

A local hands you a glass and says, “Have some water.”

Is what is in the glass water?

is the stuff in the glass water?

further reading