As someone has said, history is not events, but events that have become ideas — and ideas are of the present. The past does not change, but we do, which is why the work of history is always present, and never done. Liturgical history, therefore, does not deal with the past, but with tradition, which is a genetic vision of the present, a present conditioned by its understanding of its roots. And the purpose of this history is not to recover the past (which is impossible), much less to imitate it (which would be fatuous), but to understand liturgy which, because it has a history, can only be understood in motion.
-Robert Taft, S.J., ‘The Structural Analysis of Liturgical Units: An Essay in Methodology’, Worship 52:318.