Twenty years ago Pluto lost its planethood, and I’m partially to blame.

“Blame” is a strange word to use for what seems like a matter of mere semantics; after all, Pluto exists as an intriguing world worthy of study and exploration, regardless of labels. But after two decades in the rearview, Pluto’s demotion still stirs anger and controversy, and many people regard its change in status as a very bad thing.

You might object that your opinion of the moon has no effect on your feelings for Pluto, but equating these two objects is unavoidable for anyone seeking to manufacture a philosophically consistent reason for Pluto’s planethood. The main argument, these days, for why Pluto’s status should be restored boils down to an astrophysical version of what’s best known as “the duck test”: if something looks, walks and quacks like a duck, it’s probably a duck. In Pluto’s case, the idea is that “geophysically” it’s a planet, which simply means it looks like a planet (it’s round!) and acts like a planet (it probably once had active volcanoes, albeit of water!). Earth’s moon—which also has the advantage of being 50 percent larger than Pluto and of having volcanoes that once spewed actual lava instead of mere water—fully deserves planethood by these very same metrics.