As you've noticed, inheritance isn't really a good match for this kind of thing. It looks like it would be a better match for mixins, if Stat's methods are going to be reused in another class (like Directory).

Or you could achieve basically the same thing by having Directory and File inherit from FileSystemObject (i.e. Stat with a slightly more useful name)

Also, why are you requiring modules every time someone instantiates an Object?

update: fixed link