Sometimes, a memory does not die when it is forgotten, but when it is explicitly recollected and exposed into words.
For memories need to be preserved in their past. Without drawing them into the present, they still have the power to draw ourselves into their past.
The ghosts do not have much time for their presence on the earth – ‘Parlo; ascolta! Più tempo non ho!’, says The Statue in Don Giovanni. They can just to utter those words or to leave those signs that could make us to refuse the present for their past.
The doubt about the truly existence of ghosts and phantoms is partly justified by our current refusal to return to those persons in the way of refuting our present for their past.
They can merely mingle themselves with our present. However, without any chance to become our present. At best, they can spread moments of recollection in our present, still sufficient to decline the confidence that our present is entirely ours.