A remark about terminology: The world is the whole of physical reality. In classical (pre-quantum) physics, the world was thought to consist of one universe – something like a whole three-dimensional space for the whole of time, and all its contents. According to quantum physics, as I shall explain, the world is a much larger and more complicated object, a multiverse, which includes many such universes (among other things). And a history is a sequence of events happening to objects and possibly their identical counterparts.