Following from previous speculations (below). Observation leads to description which is the attribution of properties to entities. Entities have properties whose state only they themselves "know" authoritatively, e.g. alive. Albeit consisting of mutually ignorant entities, the universe nevertheless is the set of all properties of all entities according to their owners.
Nothing and nobody inside the universe can have an overview, which might require an additional dimension or additional dimensions. Seen from a world with an additional dimension, our universe becomes an observable object, like the snow globe in Citizen Kane maybe. To us the extra dimension is a physical barrier, absolute and unvarying to all within our universe because not observed by any, like the barrier of the third dimension to a 2-D line drawing.