Board Thread:The Panopticon/@comment-26469787-20151013042811/@comment-1398253-20151105021734

The First Doctor one said "You can't change history, not one line!" - unfortunately, the Silence don't agree. They made the cracks, and erased the events of The Next Doctor, The Stolen Earth/Journey's End, and several other episodes. But the Doctor still remembers them and is affected by them (he doesn't degenerate to a previous incarnation if the event that prompted his regeneration is averted, The Stolen Earth being one such case).