A brown and a black dog are running.
Nothing is running.
dog and nothing are not the same
exists e1 s1 x1 x2 x3.(Actor(e1,x1) & v_run(e1) & subset_of(x3,x1) & n_dog(x3) & a_black(s1) & Theme(s1,x3) & subset_of(x2,x1) & n_brown(x2))
-exists e1 x1.(Actor(e1,x1) & v_run(e1) & n_thing(x1))