It is pretty clear now that Pluto is only the nearest of a huge population of small, icy bodies that lie out past the orbit of Neptune. For historical reasons only, we should keep Pluto as a planet, but any other transneptunians, regardless of size, should be regarded as we regard the asteroids, as members of a class.

It appears the sun's satellites consist of small rocky inner bodies, large gaseous outer bodies and a halo of icy objects further out. It is not clear whether the asteroids are a fundamental component of the system or a chance structure resulting from a random event. This division of the solar system into different categories of objects may be a fundamental result of the way the system formed, or it may just be a result of sheer chance with no significance.

The original question may lead to category errors: for example, is Australia a continent? Antarctica? Is India a "sub continent". Why are Europe and Africa continents, they are just parts of Asia? Are there only two continents, EurAfroAsiA and the Americas? The word "continent" is as meaningless as the word "planet".