And there's no proof that a person isn't able to do something after their death.
Congratulations, you've just supplied one of, if not THE weakest counterargument in history. Your only basis for saying that something exists is that nobody has proved that it doesn't.
But you've done the exact same for your argument. It can go either way.
Well, have you seen a dead body/spirit moving around?
I bet you've seen a dead body laying still.
Uh, yeah, dead bodies don't move and ghosts aren't dead bodies. Ghosts are energy, in most cases this energy is invisible.