The men are climbing.
Men are climbing.
Men are climbing is an observation while saying "the men are climbing" inclines to determine that the speaker knows the men or that a specific set of people are climbing.
exists e1 x1.(n_man(x1) & Actor(e1,x1) & v_climb(e1))
exists e1 x1.(Actor(e1,x1) & v_climb(e1) & n_man(x1))