What does the term "stock characters" mean?

Read the following excerpt and answer the question.if i read the temper of our people correctly, we now realize as we have never realized before our interdependence on each other; that we can not merely take but we must give as well; that if we are to go forward, we must move as a trained and loyal army willing to sacrifice for the good of a common discipline, because without such discipline no progress is made, no leadership becomes effective.(from franklin delano roosevelt's inaugural address , )using context clues, explain what interdependence means in regards to excerpt above. be sure and write your answer in complete sentences referencing the excerpt above.