->> The validity of a definition can be established ONLY by an
->> appeal to authority.

 DW> No. Often it just boils down to common usage.

Common usage is indeed used to establish definitions.  I don't see, though,
how that fact makes my claim false.

 DW> The word
 DW> "party" was purely a noun when I was a kid. Then people
 DW> started using it as a verb, and this is now accepted usage.
 DW> The same sort of thing seems to be happening to the word
 DW> "text", in the context of sending cellphone text messages.

If someone challenged these claims, you would resort to an appeal to
authority to support them.

 DW> General usage described Pluto as a planet for decades, but
 DW> now many people prefer to call it a KBO.

Moreover, usage by the experts in the field, which in this case would be
scientists (more specifically, astronomers and other scientists working in
the field).

 DW> If this shift
 DW> becomes the norm, then Pluto *will* be a KBO rather than a
 DW> planet. It will be the same object, and there may have been
 DW> no change in formal definitions, but its accepted status will
 DW> have changed.

That was the point I was making.  If a consensus is reached among the
experts in the field, then the status will become "accepted". 
There is currently no consensus concerning Pluto's status as a planet.  It
is a point of contention.

Moreover, there is no currently accepted definition of a planet.  You could
find one in a dictionary, but that wouldn't do, since here we are talking
about a scientific definition.  Scientific definitions almost always differ
from common definitions.

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