"We are awash in time, savoring a few moments of it; we project ourselves into it, reinvent it, play with it; we take our time or let it slip away: it is the raw material of our imagination. Age, on the other hand, is the detailed account of the days that pass, the one-way view of the years whose total sum when set forth can stupefy us. Age wedges each of us between a date of birth that, at least in the West, we know for certain and an expiration...