A person on a downhill skateboard.
the person is mad
Not every person is mad.
exists x1 x2 x3.(a_topic(x1) & on(x1,x2) & n_skateboard(x2) & of(x2,x3) & n_downhill(x3) & n_person(x1))
exists s1 x1.(n_person(x1) & Theme(s1,x1) & a_mad(s1))