It would be much easier to dismiss Tisha B'Av from duty on the Jewish calendar and stop mourning the destruction of the Temple if history had come to an end. So comforting it would be to believe that the Judaism we have is the ultimate goal of a long dialectical process and that what is, is permanent.
We know that history goes on, however. Some years ago, I read an article which predicted that Judaism would continue in America for generations--but that it may not look anything like what we've been used to up to now. It made me wonder. What will go the way of the burnt-offering and the red heifer, into the realm of historical curiosities? Will Jews meet in chat rooms instead of synagogues? (In restaurants, more likely!) Will we study the collected works of Marge Piercy instead of the prophets? Will we all be involved in giving circles and social action and only let rabbis and cantors do the praying? Or, contrariwise, will an ever-tinier group keep the traditions of the synagogue alive while other people start saying, "I'm part Jewish" the way other people now confide, "I'm part Cherokee"?
On Tisha B'Av, and throughout the season of reflection that ends with the High Holy Days and begins again each year, it would be well for us to mourn--in preparation for turning the past into the future. The rabbis of 2000 years ago mourned the Temple even while they made the synagogue the hub of Jewish community. We must be ready to be as strong and creative as they.