A singer is crowd surfing.
The singer volunteered to crowd surf
A singer crowd surfing does not imply the singer volunteered.
exists p1 x1.(exists x2 x3.((x1 = x2) & n_surfing(x2) & of(x2,x3) & n_crowd(x3)) & n_singer(x1))
exists e1 x1 x2 x3.(n_singer(x1) & to(e1,x2) & n_surf(x2) & of(x2,x3) & n_crowd(x3) & Actor(e1,x1) & v_volunteer(e1))