Critical acumen is exerted in vain to uncover the past; the past cannot be presented; we cannot know what we are not.
 Henry David Thoreau, A Week on the Concord and Merrimack Rivers (1849). copy citation

Context

““I was informed by Ahmed Almatin Aljorhami, who had it from Rephâa Ebn Kais Alámiri, who had it from Saiph Ebn Fabalah Alchâtquarmi, who had it from Thabet Ebn Alkamah, who said he was present at the action.” These fathers of history were not anxious to preserve, but to learn the fact; and hence it was not forgotten. Critical acumen is exerted in vain to uncover the past; the past cannot be presented; we cannot know what we are not. But one veil hangs over past, present, and future, and it is the province of the historian to find out, not what was, but what is. Where a battle has been fought, you will find nothing but the bones of men and beasts;” source