A firefighter is working at a fire.
A fire is currently burning.
If a firefighter is working, there must be a fire burning.
exists e1 x1 x2.(at(e1,x2) & n_fire(x2) & Actor(e1,x1) & v_work(e1) & n_firefighter(x1))
exists p1 s1 x1.(a_currently(s1) & Manner(p1,s1) & exists x2.((x1 = x2) & n_burning(x2)) & n_fire(x1))