A private belief, not dispensed to anyone else, at least makes it contingently possible for _X_ to be passive and have no influence on the environment. But such does not entail inertness, since the single person holding that thought orientation can still act upon it by themselves (akin to a mentally ill individual fulfilling the commands of their inner, hallucinated demons).
Obviously the stronger held the belief is, the more difficulty in containing the conception to its figurative bottle. Unless _X_ is trivially silly or superfluous ("
I believe there are kobalds residing in the cosmos of Nodd.").
Yet if the holder deems that there are dire consequences for releasing it to others by publication or word of mouth (in terms of either retribution aganist the messenger or conviction that _X_ endangers the world), then there is personal motivation and resolve counteracting that, keeping _X_ quarantined.
But once released to the public, if it is infectious to any degree at all, then others simply discussing, promoting, or criticizing it negatively transforms into a circulating thought virus affecting behavior.
While QAnon articles of faith indicate that even extraordinarily ludicrous proposals can be contagious, they likely serve condemnatory and commending purposes with respect to foe and friend targets. Whereas, again, totally useless foolishness should be largely impotent when it comes to social transmission. Rare exceptions perhaps being those that use
earworms,
idée fixes, etc, as mediating vehicles to make the nonsensical addictive.
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