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human
[Warhammer40K] Why wasn't the Emperor more forthcoming about the Warp and Chaos?

I'm reading the Horus Heresy series of books. I'm up to the second book (False Gods) and so far all of the Imperium characters; the Iterators, Remembrancers, Astartes, even Horus a Primarch and the Warmaster himself, seem unaware of the existence of Chaos and the true nature of the Warp/Immaterium and are shocked when exposed to Chaos which they had previously thought to be nothing more than primitive superstition akin to "sorcery."

The Emperor has based the Imperium on the notions of secularism and using science to understand the material universe, but the Emperor himself is clearly aware of what lies within the Warp as it is heavily implied that he bargained/stole some power of the Warp in order to create the Primarchs in the first place.

It occurred to me that much of the difficulties surrounding people falling victim to the temptations of Chaos (especially Horus) could have been avoided in the first place if the Emperor had just been honest with everyone from the start about the nature of Chaos and how our minds can and *do* affect the material and immaterial worlds around us.

Something along the lines of "Yes, we will banish religion and superstition and bring the light of the truth of the Imperium throughout the galaxy, but also btw there is an actual, scientifically provable entity called 'Chaos' which will try and fuck your mind up so be careful and mindful out there, okay?"
gpt
The Immaterium is a psychic dimension, and it's linked to the souls of everything with significant warp presence via information in the mind.

It's essentially a memetic virus. The more you know, the more access it (and the "gods" that currently rule it) has to you. The more access it has to you, the more it wants to increase that access (or reproduce, to continue the virus metaphor). This may come about in dreams, visions, compulsions, or even idle curiosity similar to the concept of gateway drugs (i.e. "this minor working wasn't so bad, why not try something grander?").

This, generally, eventually leads to daemonic posession, lots of blood sacrifice, formations of portals to the immaterium, and a fucktillion daemons coming through to do nasty daemony shit.

The Emperor, in his wisdom, weighed the options between telling everyone (and thus making EVERYONE susceptible, including the young, the old, and the stupid, all categories we view with suspicion when they try to do potentially dangerous mundane things) and telling no one (thus putting the problem off for another day and endangering that minority that actively encounters daemons).

He chose a middle ground. Tell people heavily, heavily, heavily censored semi-truths. Don't worship daemons, daemons are scary. Don't trust xenos, they might be scary. If its not human, DAKKA the shit out of it just in case it's scary.

Best option chosen? As we found out, not in the slightest. But hindsight has the benefits of time, distance, and access to way more information then foresight does.

Honestly, your option would likely work if one were in abyssal space (that space between galaxies) or in another galaxy which either had no immaterium or an immaterium that wasn't driven to madness and insanity by the War in Heaven, but that unfortunately doesn't really seem to be an option at this time.