Dostoyevsky’s Psychological Ability
A bit of wild (very, very hypothetical) theorizing here.
So, with the reveal of Sigma’s... amnesia, we can presume that he was either created by the book (Fyodor bringing his OC to life, which seems very Fyodor) or that he was a normal person (somewhat similar to Chuuya’s mysterious origin before becoming Arahabaki’s host) completely modified by... something. The book, or Fyodor.
I’m going to run with the latter because it’s more interesting to me, and because it parallels Sigma with Goncharov (and they already have a somewhat similar mindset, as pointed out by my friend @trashyhumanespresso). It seems likely that Fyodor’s ability is something that somehow targets human brains, which fits on a meta level with Fyodor’s namesake, with his foils, and with his strategies.
Thus far in the story, we've seen Fyodor get Ace to hang himself:
Kill a kid by touching his head:
Get rid of the part of Goncharov's brain that feels sadness:
Explode a police officer's skull:
And now, he might have completely altered Sigma’s memories (I’m totally aware he very well might have used the book to do this but. It’s more interesting to me if the book is not involved lol so that’s what I’m running with but, who knows, either could be the case).
We don’t know how Fyodor’s ability precisely works--whether he manipulates their brains/exploits already-present weaknesses/targets certain parts of the brain--but it definitely involves Fyodor having to touch someone. Which brings to mind his foil also emphasized this chapter (see here for a great meta on Fyodor and Dazai’s foiling by @linkspooky): Dazai, whose ability also requires him to touch someone to enact it.
Fyodor’s match with Dazai is fascinating, as he cannot manipulate nor harm him thanks to Dazai’s No Longer Human instantly nullifying his ability. It also carries symbolic weight: while Dazai’s touch removes a person’s ability, keeping him isolated, Fyodor’s likely literally seems to bring death, which is symbolic of the nihilism he drowns himself in and that Dazai, thanks to Odasaku and his work at the AMA, resists even against his instincts towards it. Dazai is the one character Fyodor is not able to rattle, which means he’s likely key to stopping Fyodor.
In real life, Fyodor Dostoyevsky was a psychologist before Freud even wrote his theories, and he’s still held up as one of the most psychological writers in all of literature. Nietszche referred to Dostoyevsky as “the only psychologist from whom I had something to learn” (ohhh snap Freud) in Twilight of the Idols. Dostoyevsky’s works constantly explore humanity’s psychology at an individual and societal level, and are frequented with references to madness/mental illness as well.
Similarly, Fyodor is targeting the ability-users as individuals and also the larger society surrounding them. For society, he’s particularly aiming to dismantle the three-part agreement Natsume arranged between the Port Mafia, Armed Detective Agency, and the government. First the cannibalism plot pitted the mafia and the AMA against each other, and they were only able to solve it by working together. Now the government is set against the AMA via framing the AMA for that official’s murder, the mafia saves the AMA but at the cost of influencing more conflict over Mori lying about Fukuzawa’s agreement that he can take Yosano, and the mafia itself is now dealing with Tachihara’s betrayal and Gin’s injury (she is not dead), and now the AMA wants to ally with the Hunting Dogs but I doubt that’ll go super smoothly.
As for individuals, I’ll discuss Dazai more in a moment, but: Fyodor’s ability also has potential to foil another character given a fair amount of focus this arc: Yosano. His ability brings death, and her ability brings life even from already-existing pain, which it amplifies but results in them healing, which is symbolic of BSD’s overall message on life: it hurts, it can almost kill you, but it’s still healing in some ways. It is also symbolized by the butterflies associated with her, as butterflies symbolize rebirth, and as @aspoonofsugar has theorized, she also may not actually need to have them so close to death before healing them. (“Thou Shalt Not Die” is named after a poem Yosano Akiko wrote to express her pacifistic beliefs, after all, which seems interesting given that she has to hurt people to heal them.) Anyways, this would also explain Fyodor’s manipulation of the Hunting Dogs and the Port Mafia (as I’d be surprised if he didn’t know about Yosano’s past with Mori) to target her psychologically.
As for individuals, obviously Fyodor is going to target Dazai somehow at some point in an attempt to defeat him. He already surreptitiously is, through the Hunting Dogs dynamic and Tachihara’s betrayal (I doubt he didn’t know) which led to Gin being stabbed, which affects Akutagawa and thereby Dazai.
All of this brings to mind the intense parallels with Dazai/Fyodor and Mimic/Odasaku, in which all the leader of Mimic wanted was to die facing his own abilities in Odasaku and caused chaos to get it--particularly through targeting orphans under his care. Given that every arc thus far has ended in some kind of Shin Soukoku fight, plus given what happened to Gin and his promise to Atsushi, Akutagawa and Atsushi are particularly at risk here. However, they aren’t helpless, and Dazai surely plans for them to take Fyodor down--and they will, in the end.
