A man is waterskiing on one ski.
He is a professional skier.
Just because, the man is waterskiing on one ski does not imply that he is a professional skier.
exists e1 x1 x2.(on(e1,x2) & n_ski(x2) & card_eq_1(x2) & Actor(e1,x1) & v_waterskie(e1) & n_man(x1))
exists p1 x1.(n_male(x1) & exists s1 x2.((x1 = x2) & n_skier(x2) & a_professional(s1) & Theme(s1,x2)))