"As in the game of billiards, the balls are constantly producing effects from mere chance, which the most skillful player could neither execute nor foresee, but which, when they do happen, serve mainly to teach him how much he has still to learn; so it is in the most profound and complicated game of politics and diplomacy. In both cases, we can only regulate our play by what we have seen, rather than by what we have hoped; and by what we have experienced, rather than by what we have expected."