SplitInfinity
I think you misunderstood my Griffin example. I did not say the universe has the spatial and one temporal dimension, rather Griffin does(I know I'm quoting fiction excessively, so if anyone knows something that physically exists in three spatial, one temporal and a dimension that extends through alternate timelines, feel free to correct me). That is similar to saying, just because we exist in three spatial dimensions, it doesn't mean the universe has only that many.
Also, to perceive doesn't always mean to see, or to detect reflected photons. Neutrinos can't be detected by conventional methods, but that doesn't mean their existence is impossible.
Imatfaal
Yes, but I started reading the book very recently. After reading the first few pages, it occurred to me that my preconceptions about the perception of universes with lesser or more dimensions were not entirely correct. Much like how we see pseudo-3d images of our surroundings(being unable to see the backside of an opaque object) the square from flatland is unable to see 2d shapes in the detail we can see. As for Griffin, (again, pardon the fiction) he would still be able to see objects in pseudo 3d, in addition to different points in time along his current line of sight, and the alternate timelines from his current spatial perspective.