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 Ise 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 thatch and wood, are used, but the design remains exactly the same. Because it is done every twenty 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 learn 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 slipping and chopping off pieces of his body. A kindly tinsmith made replacements for each chopped-off body part until eventually, the Woodman was made entirely of tin. Is he still the same person?

Think about our own bodies. About every seven years, almost all the cells of our bodies have experienced total cellular turnover. Are we now in the same bodies we were born with, or are we in different bodies?

When a caterpillar transforms into a butterfly, is it still the same creature?

Clearly, this is a question that people across the world and throughout time have found deeply engaging. What do you think?