A group of people watch a man in a white shirt speak.
A group of people are listening to a lecture.
Just because a group of people watch a man speak doesn't necessarily mean that the group of people are listening, or that what the man is speaking is considered a lecture.
exists e2 e1 s1 x1 x2 x3 x4 x5.(in(e1,x4) & Actor(e2,x5) & v_speak(e2) & (x4 = x5) & n_shirt(x4) & a_white(s1) & Theme(s1,x4) & Theme(e1,x3) & Actor(e1,x1) & v_watch(e1) & n_man(x3) & of(x1,x2) & n_people(x2) & n_group(x1))
exists e1 x1 x2 x3.(to(e1,x3) & n_lecture(x3) & Actor(e1,x1) & v_listen(e1) & of(x1,x2) & n_people(x2) & n_group(x1))