the past is not strictly unalterable

As Augustine correctly saw, one cannot imagine, and there could not be, any entirely discrete past event unaffected by what came later, just as, to use his example, a note in music is only situated and defined by its place in a sequence, such that the end of a musical composition still to be heard can change the nature of what we have already heard. Certainly there are limits to alteration, even though they cannot be specified: the note remains this note, however far the new relations it enters into may re-disclose it. Nevertheless, these reflections reveal that the past is not strictly unalterable and that the remembered past, although provisional and revisable, is not a sort of hypothesis that can never be confirmed, but is rather the ontologically real past.

—John Milbank, Being Reconciled (2003)