Everyone realizes, of course, that the question of whether Pluto
is a "planet" is not a well-defined scientific question, since
"planet" is not a well-defined concept in the sense of proton
and electron or even species (defined in terms of fertile
interbreeding) and star (defined in terms of nuclear fission).
It's a term of convenience that we like using to group together
the "major" objects circling a star, inherently having fuzzy
boundaries. That being said, I thought Pluto should be excluded
from the club, or more precisely that my sense of how the term
"planet" is most conveniently used suggests excluding it. In
addition to all the differences between it and both the rocky
inner planets and the gas giants, the fact that a whole bunch of
other objects, not easily distinguished from Pluto, may be out
there, suggests to me that we would have too many planets from a
convenience standpoint if we didn't give Pluto the old heave-ho.
And calling the asteroid Ceres a planet, as the earlier
definition would have do