Human beings cannot live without hope. Unlike the animals, we are blessed - or cursed- with the ability to think about the future and to fear our actions to shaping it. So essential is this to human life that human beings cannot live with our hope, without something to live for, without something to look forward to. To be without hope, to have nothing to live for, is to surrender to death in despair. But we can find all sorts of things to live for and we can hope for almost anything: for some measure of success or security or for the realization of some more or less modest ambition; for our children, that they might be saved from our mistakes and sufferings and find a better life, than we have known; for a better world, throwing ourselves in to politics or medicine or technology so that the future generations might be better off. Not all these forms of hope are selfish; indeed, they have given dignity and purpose to the lives of countless generations.
But one of the reasons we read the Old Testament during Advent is to learn what to hope for. The people of the Old Testament had the courage to hope for big things: that the desert would be turned into fertile land; that their scattered and divided people would eventually be gathered again; that the blind would see, that the deaf would hear, the lame walk; that not only their own people but all peoples of the earth, would be united I the blessings of everlasting peace. Clearly, their hopes were no different from ours or from any human being's; lasting peace, tranquil lives, sufficiency of food, and an end to suffering , pain and misery.
Thus we hope for the same things as the Old Testament people, for their hopes are not yet realized. But we differ from them in two ways. First, the coming of Jesus in history, as a partial fulfillment of God's promises, immeasurably confirms and strengthens our hope. Secondly, we differ from the Old Testament people because Jesus has revealed to us that God is not afar off, but is already in our midst. Hence the importance in the Advent liturgy of John the Baptist and of Mary: because they recognized the new situation, they serve as models for the Church in discerning the presence of our Savior in the world.
Taken from " the Spirit of Advent," Mark Seale, Notre Dame Center for Liturgy, Notre Dame, IN