Hi, people. New here. Found this site because I was interested in the planet debate.

Although the IAU haven't defined exactly what they mean by 'cleared the neighbourhood of its orbit', it is a necessary criteria for an object in the solar system to be a planet and that also by the IAU definition there are eight planets (note, not at least eight, or eight known - exactly eight) in the solar system.

To be internally self-consistent, whatever is the exact meaning of 'cleared the neighbourhood around its orbit' in the IAU definition, applying that meaning has to result in Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune having cleared the neighbourhood around their orbits. So, only meanings of 'cleared the neighbourhood around its orbit' that have that result can be valid!

It might be the case that no-one will be able to come up with a definition of 'cleared the neighbourhood arounds its orbit' that means that those eight objects have done so. In which case the IAU definition is internally self-contradictory, and the IAU will have to go back to the drawing board!