Why do descriptors (and thus properties) only work on attributes.

[Paul Rubin]

Antoon Pardon <apardon at forel.vub.ac.be> writes:
> Can anyone explain why descriptors only work when they are an attribute
> to an object or class.  I think a lot of interesting things one can
> do with descriptors would be just as interesting if the object stood
> on itself instead of being an attribute to an other object.

How would that work?