Every Sunday, millions of Latter-day Saints participate in a ritual whose logic is more radical than it first appears.

They gather, they take bread and water in remembrance of a person who lived two thousand years ago, and they covenant to keep his commandments as though those commandments govern their lives today.

They are, in the precise sense, acting as people whose identity extends across time: backward to Gethsemane, forward to the judgment, outward to every generation connected by the same ordinance.