The Pleasure of Finding Things Out

by Richard P. Feynman

For instance, the scientific article says, perhaps, something like this: “The radioactive phosphorus content of the cerebrum of the rat decreases to one-half in a period of two weeks.” Now, what does that mean? It means that phosphorus that is in the brain of a rat (and also in mine, and yours) is not the same phosphorus as it was two weeks ago, but that all of the atoms that are in the brain are being replaced, and the ones that were there before have gone away. So what is this mind, what are these atoms with consciousness? Last week’s potatoes! That is what now can remember what was going on in my mind a year ago–a mind which has long ago been replaced. That is what it means when one discovers how long it takes for the atoms of the brain to be replaced by other atoms, to note that the thing which I call my individuality is only a pattern or dance. The atoms come into my brain, dance a dance, then go out; always new atoms but always doing the same dance, remembering what the dance was yesterday.