A city street is illuminated by lamps at night.
There is nothing to see.
It is impossible that there is nothing to see if the street is illuminated.
exists e1 x1 x2 x3 x4.(at(e1,x4) & n_night(x4) & Actor(e1,x3) & n_lamp(x3) & Theme(e1,x1) & v_illuminate(e1) & n_street(x1) & of(x1,x2) & n_city(x2))
exists p1 x1.-exists p2 x2.((x1 = x2) & Topic(x2,p2) & exists e1.(Actor(e1,x2) & v_see(e1)) & n_thing(x2))