The bike is secured to a metal post.
The bike cannot be stolen.
It is impossible to know if the bike cannot be stolen from the post.
exists e1 x1 x2 x3.(n_bike(x1) & to(e1,x2) & n_post(x2) & of(x2,x3) & n_metal(x3) & Theme(e1,x1) & v_secure(e1))
exists x1.(n_bike(x1) & -exists e1 p1.(exists e2.(Theme(e2,x1) & v_steal(e2)) & Topic(e1,p1) & Actor(e1,x1) & v_can(e1)))