As time went by, it became increasingly clear that it wasn't Pluto which was responsible for Neptune's weirdness at all, mainly because it was a bit titchy and frail. It seemed to be made of ice and rock, mainly the former, and was in fact not even strong enough to hold itself together and was in fact a whole system of objects orbiting each other like this:
In the end they decided it wasn't a planet after all, but a dwarf planet. There was a petition recently to reinstate it. There were fairly good reasons for not seeing it as a planet, including the fact that if they did, Sedna and Eris, which are further out, would also have to be planets and in the end there would probably turn out to be loads and being a planet wouldn't be special any more, so it does make sense. However, it's also unlikely that if it hadn't still been called a planet at the time, NASA would've sent the New Horizons probe, which is due to get there next year, thither. Oddly, it seems a lot more exciting if a ball of ice is called a planet when it gets visited by a spacecraft than if it isn't.
This may surprise you, but this blog post isn't really about space at all. When Clive Tombaugh looked at the photos and saw that a white dot was in two different places on two different nights back in 1930, what he saw didn't change just because it was assumed it was a planet. There's a whole cosmic cairn of calculi out there, some of which are called planets and some of which aren't, and it's us that label them. Pluto probably doesn't care. The Usurians won't care either, probably, but you never know.
What this is about really is the question of natural kinds. I'm not going to make the obvious connection but the other one. I look out of the window and see this:
which is among other things a Hydrangea, a Buddleia, a Fuchsia (yum!) and some ivy, or a load of plants, or a load of organic matter, or a load of baryonic matter. Or stuff. Or something I can't even begin to comprehend and never will and can never know that I'm failing to grasp. Many botanists would say I'm looking at several species of dicotyledonous plants, particularly if they take their work home with them. If it turned out they were wrong, it might still be that there were still natural kinds of things "out there" which existed whether or not they or anyone else thought about them. But the matter depicted in this photo wouldn't care and would still be what it was unless it got involved in human culture by, for example, being cut off and made into a wedding bouquet as the plant on the left was a few weeks ago.
My brain might be of a natural kind, or it might not be. You can see where I'm going with this so I won't carry on in that vein. Unlike Pluto, which probably doesn't care, people really do quite often care what kind they are, and of course other people do too. Whether or not natural kinds exist, kinds can be made to exist by people, and that does matter. It would matter on Pluto if it turned out the Usurians couldn't claim housing benefit because only people who live on planets were entitled to, but right now it doesn't. At some point it might, and of course if they possibly could, I'm sure the Usurians would want to claim that, although they're more likely to try to claim tax back on Pluto as a legitimate business expense or something. But they would care. Bye.