Noosphere

A noosphere was the limit set by a species' technology, biology, and psychology on the information it could find and understand. If a thing or idea existed beyond a species' noosphere, then that thing or idea was either undetectable or incomprehensible to that species.

Pierre Teillhard de Chardin defined a noosphere as the living interaction of thought and culture, complementing a world's geosphere and biosphere. Mictlan notably had a noosphere with neither a biosphere nor a geosphere to support it.

Certain dead-time states were considered outside of all possible noospheres.

The Mal'akh were specially tuned-in to humanity's noosphere. (PROSE: The Book of the War)

The Great Houses' noosphere
The Great Houses' noosphere was the entire Spiral Politic, since it was specifically engineered to be an extension of their will. However, for unknown reasons, the Houses had difficulty penetrating or even just observing certain areas of the Spiral Politic, particularly near the frontier in time. The Book of the War speculated that the Houses' modifications on their own bodies during the War were attempts to produce a mutation that could see beyond this edge of their noosphere.

The enemy was thought to come from beyond the Houses' noosphere, since it operated on principles that they weren't built to understand. Chatelaine Thessalia predicted that their first attack would be on the Houses' noosphere; the casts and, later, the babels were designed to protect it. (PROSE: The Book of the War)