A man operating a furnace.
A person lights a flame.
A man is a person operating a furnace who can do this only after lighting it. A furnace emits flame.
exists e1 x1 x2 x3.(a_topic(x1) & Theme(e1,x3) & Actor(e1,x2) & v_operate(e1) & n_furnace(x3) & (x1 = x2) & n_man(x1))
all x1.(n_flame(x1) -> exists x2 x3.(a_topic(x2) & for(x2,x1) & Time(x2,x3) & n_light(x3) & n_person(x2)))