A cogitator is the Imperium's equivalent of a computer, a data-processing engine used to calculate, store information, and control machinery across the galaxy. Yet a cogitator is nothing like a sleek modern computer; it is a bulky, often massive contraption of clattering mechanisms, glowing valves, and brass fittings, its workings shrouded in ritual and incense. To the people of the 41st millennium, the inner logic of such machines is a mystery, and coaxing answers from a cogitator is as much an act of worship as of engineering.
Cogitators run everything from the targeting systems of weapons and the controls of starships to the vast archives of Imperial bureaucracy. Operating them properly requires the correct rites, prayers, and the burning of sacred oils, for the Imperium treats its machines as vessels housing a spirit that must be appeased rather than merely programmed. A poorly maintained cogitator may produce errors, or worse, and so its care is taken with deadly seriousness.
The tech-priests of the Adeptus Mechanicus are the true masters of these machines, guarding the knowledge of their construction and repair as sacred lore. For everyone else, a cogitator is a temperamental oracle to be consulted with caution and respect. Its clicking relays and flickering runescreens are a familiar feature of Imperial life, a reminder that mankind now uses technology it can operate but no longer truly understands.