I'm Gretchen Rubin and this is a little happier.

Throughout the ages, people have considered a question.

If an object is replaced piece by piece, once all the original components have been replaced, is it the same object?

Or is it something different?

This question appears in many different

guises and in many different times. For instance, according to Greek legend, King Theseus,

the mythical founder of Athens, slayed the terrible minotaur and then sailed back to Athens.

The Athenians preserved his ship, and any time an

old plank decayed, the Athenians replaced it with new timber. This practice presents the

question that's known as the ship of Theseus paradox. After several centuries of maintenance,

if each individual part of the ship of Theseus had been replaced, piece by piece,

was the ship still the same ship? In Japan, the Grand Shrine of Isay is an extremely important

Shinto shrine that is at once ancient and newly made. For about the last 1,300 years, every two decades,

in a sacred practice, the wooden structure is torn down and a new one is built all according

to the original traditional design, with no new technology or changes in procedure.

Ephemeral materials such as fatch and wood are used, but the design remains

exactly the same. Because it is done every 20 years, the knowledge of how to rebuild the shrine

properly, according to the old ways, can be handed down through time. Does the shrine remain the old

shrine, or is it a new shrine? And here's a familiar example from children's

literature. In L. Frank Baum's beloved novel, The Wonderful Wizard of Oz, we learned why the tin

woodman is made of tin. He started out as an ordinary woodsman named Nick Chopper, but the

wicked witch of the east enchanted his axe so that it kept

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