The navigator fantasy

There's a familiar idea that floats around discussions of higher dimensions: that in a 4+1 universe, you'd be able to see all the possible paths your life could take, branching out from each moment, and pick the one you want. David finds this silly, and the reason he finds it silly is worth slowing down on.

Run the analogy one dimension lower. Imagine a 2+1 being trying to picture what life in a 3+1 universe would feel like. The naive version of the fantasy says: in 3+1, you'd be able to see different paths for your life laid out around you, and travel between them.

But this is ridiculous. It presupposes that everyone else in this 3+1 universe still exists as if it were a 2+1 universe, and the subject is the only one who has the magical powers to move though 3 dimensional space.

We know this isn't how it works, because we live in 3+1. Everyone around us is also a full 3D observer. Nobody gets to be the sole navigator while everyone else stays flat. The dimension, if it's real, belongs to everyone.

So, the idea of a life, of a quale, exists in 3 dimensions. We are all ontologically equal.

That ontological equality is the move. Once you grant it, the selfish version of the higher-dimensional fantasy — I browse the menu, they are scenery — collapses. You can't move downstairs in a five-story building and experience a different life, because the people downstairs got upgraded too. They have their own lives, in three dimensions, same as you.

There is one wrinkle worth flagging. When people talk about a 4+1 universe with branching paths, they're often not really talking about an extra spatial dimension. They're gesturing at something about time — the idea that the future is a tree of possibilities rather than a line, in the Everett or garden-of-forking-paths sense. That's a different claim, and the spatial analogy doesn't directly defeat it.

But the same argument runs in temporal clothing. If the branching is real, every conscious being in the structure is also branching. Every fork contains full observers with their own continuity. There is no privileged navigator, in time or in space. The fantasy needs someone to be the chooser while everyone else holds still, and that role doesn't exist.

The dimension belongs to everyone, or to no one.