Theory and Analysis:Eva-00's Soul

Ritsuko reveals in Episode 23 that in order to function all Evangelions contain a human soul, and it is heavily implied that that soul has to be the mother of the pilot. Eva Unit-01 contains the soul of Shinji's mother Yui, and Eva Unit-02 contains (the maternal part of) Asuka's mother Kyoko. It is implied that all of the other potential Eva pilots in Class 2-A have dead mothers, and that Toji Suzuhara's mother is dead. Thus when Toji becomes the pilot of Eva Unit-03, it's a strong possibility that Toji's mother's soul was inside of it. However, "Rei Ayanami" is a clone of Yui Ikari: Rei does not have a mother. Thus, the identity of the soul contained inside of Eva Unit-00 is a bit of a conundrum, and remains one of the officially unanswered mysteries of the series.

However, evidence and clues as to the identity of the soul in Eva Unit 00 appear several times during the series, particularly in Episode 05, Episode 14, and also Episode 26.

The Evidence

To begin with, a large piece of evidence is that Eva Unit 00 is just a Prototype and often loses control or acts "buggy", implying that there is something different about it. As stated above, Rei has no mother, so unlike Shinji and Asuka, her mother's soul cannot be the one in her Eva. That seems to be the most obvious explanation as to why Rei's Eva Unit does not always function properly.

Some have also theorized that Eva Unit 00 simply has no soul inside of it at all; however, Ritsuko seemed clear in Episode 23 that an Evangelion requires a human soul to function, and she said that each Eva contains a human soul.

Finally, the exact nature of who or what "Rei Ayanami" is a matter for discussion in and of itself, though it overlaps with discussion of the identity of the soul in Unit 00. Nonetheless it can at least be said that Rei is a physical clone of Yui Ikari, which acts as a vessel for the soul of the Seed of Life Lilith.

Episode 05

• During a startup test, Eva Unit 00 goes out of control.
  • While berserk, Eva 00 repeatedly punches a glass window which Gendo Ikari is standing directly behind.
  • Eva 00 seems to reject Rei, and in the process Rei gets severely injured when her Entry Plug auto-ejects.
  • When Misato Katsuragi directly asks Dr. Ritsuko Akagi why Eva Unit 00 lost control, the following exchange takes place:

Misato: "So, what caused the accident during the last experiment?"
Ritsuko: "We still don't know. However, we believe that mental instability on the part of the pilot was a primary cause."
Misato: "Mental instability? In Rei?"
Ritsuko: "Yes, her mind became much more disturbed than we had anticipated."
Misato: "So what happened?"
Ritsuko: "I don't know. But it could be..."
Misato: "Did something occur to you?"
Ritsuko: (to herself) "No...that can't be it..."

Episode 14

A "mutual compatibility experiment" is conducted to see if Shinji Ikari can synchronize with Eva Unit 00, and it goes berserk again.

• Right after Shinji synchronizes with Eva-00, he sees a vision of a rapid burst of images of Rei, saying: "What is this?! Something's trying to get directly into my brain. Ayanami? Rei Ayanami? This impression is Rei Ayanami, isn't it? Ayanami?...or maybe not?"
• Eva Unit 00 goes berserk, and repeatedly punches a glass window which Rei Ayanami is standing directly behind. Misato even openly wonders "could it be that Unit 00 just tried to kill Rei?"
• However, after Misato finishes talking to Ritsuko, Ritsuko thinks to herself: "The person Unit 00 wanted to hit was me. I'm sure of it."
  • There's nothing to say it wasn't trying to hit both of them.

Episode 26

• While Rei is going through Instrumentality, she sees a vision of the same wide-eyed "Rei" that Shinji saw in Episode 14 when he was in Eva Unit 00.
  • A complication arising from this is the "do the original Episodes 25 and 26 count as canonical, or where they rendered non-canon by The End of Evangelion?". However, the information relating directly to Rei from Episode 26 does not seem to be particularly changed by anything in The End of Evangelion.

Analysis

Eva Unit 00 appears to have tried to attack Gendo Ikari, Dr. Ritsuko Akagi, and its own pilot Rei Ayanami, at various times. Also, based on Ritsuko's comment as she trailed off in Episode 05, Ritsuko knows more about the situation than she is telling Misato (of course), and there is some vital hint which she considers before dismissing as impossible (obviously implying that that is actually probably the cause). As Nerv's head scientist, Ritsuko herself actually probably knows whose soul is in Eva Unit 00, as she went on to state to Misato that all Evas have a soul inside of them, and Ritsuko knows that Rei is really part of a series of clones. Eva 00 also seemed to violently reject Shinji, but this may not have been because of Shinji specifically, but just because someone other than her normal pilot was trying to synch with her. Finally, Shinji sees an "impression" of what he thinks is Rei while synchronized with Eva Unit 00, but ends by saying "...or maybe not", hinting that the "impression" he sees isn't really the "Rei" he knows.

Naoko Akagi?

A theory which circulated around the internet for some time, soon after the series aired, was that the soul in Eva Unit 00 is actually that of Gehirn's chief scientist, Ritsuko's mother, Dr. Naoko Akagi. The basis for this theory was that the three people Eva 00 attacks -- Gendo, Ritsuko, and Rei Ayanami (Rei II) -- are all personal enemies of Naoko Akagi. Gendo fooled Naoko into thinking he loved her, but was really only using her (as revealed in Episode 21). When Rei I told Naoko this, in a fit of rage and harsh realization, Naoko strangled Rei I to death. Naoko might have seen Rei as "competition" for Gendo's affections, because Gendo really still loved Yui, and Naoko was starting to make the connection that there was a link between Rei and Yui. At the same time, Naoko would want to lash out at Gendo himself, even more than Rei, because he had used her. Ritsuko actually got along fairly well with her mother professionally, and at times they seemed to be on good speaking terms in the flashbacks from Episode 21, but throughout the series (specifically Episode 13) Ritsuko says that she got along with her mother professionally but they really had a tumultuous personal relationship. Now, Ritsuko has been carrying on an illicit relationship with Gendo just as her mother used to, and Naoko might see this as "competition". Indeed, during The End of Evangelion, the Magi supercomputer Casper, based on the personality-aspect of Naoko as a woman, sided with Gendo over Ritsuko. Thus, all three people that Unit 00 directly tried to attack are people who Naoko Akagi would be trying to attack if her soul were in an Eva.

Counter-arguement

The "Unit 00's soul is Naoko" theory was popularized by several fansites for a while, but as time went on it generally fell out of favor for several reasons.