Tim May wrote
If you mean that "many presents" have "many pasts," yes. But the current present only has a limited number of pasts, possibly just one. (The origin of this asymmetry in the lattice of events is related to our being in one present.)
I mean one (many?) present has many pasts as well as many futures. Many pasts are fundamentally caused by quantum uncertainty in memory devices; many presents are caused by uncertainty in observation devices; many futures are caused by uncertainty in the controlling devices. The past cannot be ascertained precisely just as the future cannot be predicted precisely. Our consciousness is a fuzzy point in the many world. It has an infinite number of pasts and an infinite number of futures, an everbranching tree toward the past and an everbranching tree toward the future. Taking many observer moments together, I view the many world more as a lattice then as a tree. Thus navigation in the many-world makes sense.