Having preserved and altered across the generations to our own time, they are sure to continue into the future. Skills like writing, and devices like bureaucracy are even older than Christianity, and concerns that bother us still can be read into the cave paintings left behind by Stone Age hunters as much as twenty thousand years ago. Only an acquaintance with the entire human adventure on earth allows us to understand these dimensions of contemporary reality. Memory is not something fixed and forever. As time passes, remembered personal experiences take on new meanings.
Collective memory is quite the same.
Historians are always at work reinterpreting the past, asking new questions, searching new sources and finding new meanings in old documents in order to bring the perspective of new knowledge and experience to bear on the task of understanding the past. This means, of course, that what we know and believe about history is always changing. In other words, our collective, codified memory alters with time just as personal memories do, and for the same reasons. When teachers of history admit that their best efforts at understanding the past are only tentative and sure to altered in time to come, skeptics are likely to conclude that history has no right to take student time from other subjects. Then surely, the changing perspectives of historical understanding are the very best introduction we can gave to the practical problems of real life.