By empty, I meant a person who does not think [for him or her self]even though she or he has the capacity to think.

In this sense, people have empty minds if they accept whatever anyone else tells them to accept without "giving it a moment's thought". They are empty headed because they are too lazy to think.

Of course, one's mind could be cluttered with American Idol soap opera gossip. But it seems to me that this world would be a better place if people "messed" with ideas more, turning them inside out and up and down, stretching ideas, thought about them outside their separate boxes, even if in the process those boxes became battered and torn. What then would be done is to create a better, more flexible, more expansive box or merge it with another box that still is intact.
In doing so, people's minds might become "cluttered". And in my opinion, that clutter would be [or maybe I should say "could be"]
a good thing.

I should also say that I believe that organized clutter is better than disorganized clutter. For me, that's a worthy goal.