A zebra is nibbling on some grass.
the zebra is hungry
Just because a zebra is nibbling on grass doesn't mean that it is hungry.
exists e1 x1 x2.(on(e1,x2) & n_grass(x2) & Actor(e1,x1) & v_nibble(e1) & n_zebra(x1))
exists s1 x1.(n_zebra(x1) & Theme(s1,x1) & a_hungry(s1))