A person working in a field.
The person is a slave.
working in the field does not make a person a slave.
exists e1 x1 x2 x3.(a_topic(x1) & in(e1,x3) & n_field(x3) & Actor(e1,x2) & v_work(e1) & (x1 = x2) & n_person(x1))
exists p1 x1.(n_person(x1) & exists x2.((x1 = x2) & n_slave(x2)))