Theory and Analysis:Eva-00's Soul: Difference between revisions

From EvaWiki
Jump to navigation Jump to search
 
(96 intermediate revisions by 12 users not shown)
Line 1: Line 1:
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 Zeppelin Soryu|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 [[Evangelion Unit-00]] is a bit of a conundrum, and remains one of the ''officially'' unanswered mysteries of the series:  to this day, series creator [[Hideaki Anno]] has given no official answer on the topic.
[[Ritsuko Akagi|Ritsuko]] reveals in [[Episode 23]] that, necessary to function, all [[Evangelions]] contain a [[Lilin|human]] [[soul]], and it is heavily implied throughout the series and explicitly stated in the [[Classified Information (Translation)|Classified Information]] that that soul must be the pilot's mother.  Eva-01 contains the soul of Shinji's mother [[Yui Ikari]], and Eva-02 contains at least the maternal part of Asuka's mother [[Kyoko Zeppelin Soryu|Kyoko]].  It is implied that all of the other potential Eva pilots in [[Class 2-A]] have dead mothers and, likewise, that [[Toji Suzuhara]]'s mother is dead.  Thus, when Toji becomes the pilot of Eva-03, it is implied that it contains his mother's soul.  However, [[Rei Ayanami|Rei]] was created from the [[Angel]] [[Lilith]] and the remains of Yui Ikari, and thus does not have a mother.  The identity of the soul contained within [[Evangelion Unit-00|Eva-00's]] core is never ''directly'' stated in the series, however, evidence and clues as to the identity of the soul in Eva-00 appear several times during the series, particularly in [[Episode 05]], [[Episode 14]], [[Episode 23]] and [[Episode 25]] and also [[Episode 24]].


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 13]], [[Episode 23]], and [[Episode 26]].
==The Evidence==
Rei's Eva-00 was the first working Prototype out of a very long string of failures; it goes out of control twice and is "buggy", often returning errors when under testing. As stated above, Rei has no mother, so unlike Shinji and Asuka, her mother's soul cannot be in her Eva.  Aside from the construction defects, the soul inside Eva-00 not being Rei's mother is the likely explanation as to why Rei's Eva does not always function properly.


==The Evidence==
===Episode 5===
During a startup test, Eva-00 goes berserk.
[[File:05 C031g.jpg|thumb|left|Unit-00 punches the window.]]
*While berserk, Eva-00 repeatedly punches a glass window behind which [[Gendo Ikari]] is standing. Ritsuko is further behind the glass but in plain sight of the Eva. 
*Eva-00 rejects 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-00 lost control, the following exchange takes place:
::'''Misato:''' So, what caused the accident during the last experiment?<br>'''Ritsuko:''' We still don't know.  However, we believe that mental instability on the part of the pilot was a primary cause.<br>'''Misato:''' Mental instability? In Rei?<br>'''Ritsuko:''' Yes, her mind became much more disturbed than we had anticipated.<br>'''Misato:''' So what happened?<br>'''Ritsuko:''' I don't know.  But it could be...<br>'''Misato:''' Did something occur to you?<br>'''Ritsuko:''' No. That can't be it.
 
===Episode 14===
[[Image:14 C062B anim.gif|right|thumb|Distorted Rei seen by Shinji inside Eva-00. (Click to see animation.)]]
A unit interchangeability test is conducted to see if Shinji can synchronize with Eva-00 and if Rei can synchronise with Eva-01 so Nerv can implement their plan for the [[Dummy Plug]]. During this test Eva-00 goes berserk.
*As soon as Shinji is connected via the A-10 nerve to Eva-00 he sees a rapid burst of images of Rei. Shinji says:
::'''Shinji''': What is this? Something's trying to get directly into my brain. Ayanami? Rei Ayanami? This impression is Rei Ayanami, isn't it? Ayanami? Isn't it her?
 
When this Rei reappears in Ep. 25, she is explicitly identified in the script as Rei 1.


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.
*Eva-00 goes berserk, and repeatedly punches a glass window behind which Rei is standing.  Misato speculates "could it be that Unit-00 just tried to kill Rei?", but after Misato finishes talking to Ritsuko, Ritsuko thinks to herself: "The person Unit-00 wanted to hit was me. I'm sure of it." Ritsuko is in a position to know what soul is where; Misato is not.
*Eva-00 seems to mistake Ritsuko for her mother Naoko; In the "Eva point-of-view" shots Eva-00 sees Ritsuko with Naoko's dark hair. It is unlikely that this is just an animation error because the other details of Ritsuko's appearance and clothing are accurate, such as her unbuttoned lab coat and blue shirt.  


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.   
{{MontageBox
|float = left
|columns = 4
|title  =
|colour  =
|image1  = [[Image:Evaeyeview2.jpg|thumb|180px|Possible Eva-00 targets.]]
|image2  = [[Image:Evaeyedetail2.jpg|thumb|170px|Observe Ritsuko's hair color.]]
|image3  = [[Image:Ritsblueshirt.jpg|thumb|none|Note the details in both images. Blue shirt, open lab coat.]]
|image4  =
|image5  =
|image6  =
|image7  =
|image8  =
|image9 =
|image10 =
|caption =
}}
{{-}}


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 23===
[[Image:Armisael-ReiBleeding.jpg|left|200px|thumb|[[Armisael]] speaks with [[Rei]] during [[Episode 23]].]]
*The Angel [[Armisael]] begins to merge with Eva-00 and makes direct contact with Rei's mind. When Rei first feels Armisael contacting her mind, she thinks to herself: "Who's there? '''Me? The me inside the Eva?''' No, I can sense that there's someone other than me." This reinforces the evidence from Ep. 14 that Eva-00's soul is somehow connected to Rei.


===Episode 05===
===Episode 24===
*During a startup test, Eva Unit 00 goes out of control.
*This episode is important for our understanding of the synchronisation process between Rei and Eva-00. Kaworu is the only other example of a Seed of Life's soul present in a [[Lilin]] vessel besides Rei who pilots an Eva. Kaworu synchronises with Eva-02 without its core being reconfigured and later pilots Eva-02 while not present in the Entry Plug. The reason for this is that Kaworu is made of the same matter as Eva-02.
**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?"<br>'''Ritsuko:''' "We still don't know.  However, we believe that mental instability on the part of the pilot was a primary cause."<br>'''Misato:''' "Mental instability?  In Rei?"<br>'''Ritsuko:''' "Yes, her mind became much more disturbed than we had anticipated."<br>'''Misato:''' "So what happened?"<br>'''Ritsuko:''' "I don't know.  But it could be..."<br>'''Misato:''' "Did something occur to you?"<br>'''Ritsuko:''' (''to herself'') "No...that can't be it..."


===Episode 13===
[[Image:24 C153 npc c mid.jpg|thumb|right|I don't need no entry plug!]]
Also of note is that when Rei's [[Simulation bodies|simulation Eva body]] was infected by the Angel [[Ireul]] in [[Episode 13]], it tried to attack a control box which Ritsuko and Misato were in, but not Gendo.  Misato was not present when Eva 00 went berserk in Episode 05, so she would seem to be just a bystander.  However, ''every'' time Eva 00 has lost control it tries to attack Ritsuko (among others).  Still, this may not be particularly significant to finding out whose soul is in Eva 00, because this was an attack instigated by the infection of an Angel, not by Eva 00 itself.  Further, Ritsuko was already one of the people Eva 00's attacks were directed against in Episode 05 and Episode 14, so the incident in Episode 13 doesn't ''really'' add any "new" insights or information, but it might have led Ritsuko to the conclusion that the berserk Eva was indeed after her.


===Episode 14===
:::'''Kaworu''': The Eva are made of the same body as I am. Because I am born from Adam as well. I could merge with them, if only they didn't have souls. Unit-02's soul has shut itself away for now.
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 23===
*Rei is made of the same matter as Eva-01 which was grown from Lilith, but not Eva-00. This suggests that Rei successfully synched with Eva-01 in Ep. 14 only because Yui allowed it. Yui has not shut herself away, and successfully rejects synching with Rei in Ep. 19.
The Angel [[Armisael]] begins to merge with Eva Unit 00, and makes direct contact with Rei's mindWhen Rei first feels Armisael contacting her mind, she thinks to herself: "Who's there? Me? The me inside the Eva. No, I can sense that there's someone other than me."


===Episode 25===
===Episode 25===
*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''.
[[Image:Floatinghead.jpg|left|thumb|200px|The wide-eyed Rei in [[Episode 25]].]]
*During Rei's experience of Instrumentality she sees a vision of the same wide-eyed "Rei" that Shinji saw in episode 14 when he was in Eva-00.  The script for episode 25 explicitly identifies this Rei as Rei 1.
 
===Supplemental evidence===
*The [[Classified Information (Translation)|Classified Information]] files that were included with the [[Neon Genesis Evangelion 2]] videogame state:
::"A unit called a [[core]] is used to eliminate the discrepancies in Eva, a human being with the body of a god and a soul. The soul of the pilot's mother, which is placed within the core, acts as a medium and makes piloting possible... Due to difficulties encountered in the development of Eva-00, the core's system is poorly constructed, and she falls behind in performance capacity as a result. Another reason for her inferiority is that Eva-00's pilot, Rei, does not have a mother."
 
Also, in an [http://eva.onegeek.org/pipermail/evangelion/2006-November/003855.html interview with Sadamoto in ''Der Mond''], Sadamoto outright says "the dead mother is inside the robot, which is operated by mental/psychical bonding with the child").
 
[[Image:Snap066i.png|right|thumb|Rei 1 speaking with Rei 2 during the [[Leliel]] battle.]]
 
*In the actual [[Neon Genesis Evangelion 2]] PSP port video game (which Anno also worked on), when whichever pilot being played as is about to break free from [[Leliel]], the soul of the Eva contacts the pilot. In the case of Shinji, Asuka, and Toji, they see their mothers, while Kaworu is able to force Eva-04 out of Leliel. However, Rei 2 sees the distorted Rei visage shown in [[Episode 14]] (considered to be a hint of Rei 1 being inside Eva-00) and [[Episode 25]] and is designed with "????" as she speaks to Rei.
 
[[Image:Snap067.png|left|thumb|Rei 1 designated as ???, tells Rei 2 that she must "Retrieve the [[Fruit of Life]] from [[Adam]]" during the [[Leliel]] battle.]]


==Analysis==
==Analysis==
Eva Unit 00 appears to have tried to attack Gendo Ikari, Dr. Ritsuko Akagi, and its own pilot Rei Ayanami, at various timesAlso, 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 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.  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.
Eva-00 could have been aiming for Gendo Ikari, Ritsuko Akagi, or its own pilot Rei Ayanami, during either berserk incidentBased on Ritsuko's comment as she trailed off in Episode 05, Ritsuko knows more about the situation than she is telling Misato and there is something of importance which she considers before dismissing as impossible. As Nerv's head scientist, Ritsuko must herself know whose soul is in Eva-00, and she herself stated that all Evas have a human soul inside them. She knows that Rei is just one of a series of clones and possibly knows about the fate of Rei 1 as well.


Finally, that Ritsuko pauses to consider some higher significance (before dismissing it from her mind as impossible) to Eva 00's targeting of the control box specifically containing Gendo and Ritsuko in when it goes berserk Episode 05, seems to ''heavily'' imply that the soul in Eva Unit 00 is that of someone significant; i.e. if Eva 00 ''has'' to have a soul (because of Ritsuko's comments in Episode 23), they didn't just "grab a random person off the street", as it were, to use their soul in Eva 00. The soul in Eva Unit 00 seems to have some significance.
Eva-00 also seemed to violently reject Shinji, although this may not have been because of Shinji specifically, but rather because someone other than her normal pilot was trying to synch with her.  Shinji sees an "impression" of what he thinks is Rei while synchronized with Eva-00, but ends by saying "...isn't it her?", hinting that the "impression" he sees isn't the "Rei" he knows. Rei similarly speaks of "the me inside the Eva".  


===Naoko Akagi?===
What does all this mean?  There have been many theories over time, but of the three most popular, two have generally fallen into disfavor after many years of sometimes contentious debate.  We will address those two first.
 
==Formerly Popular Theories==
 
===Eva-00 Has no Soul?===


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 herRitsuko 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.
It has been theorized that Eva-00 simply has no soul at all, and that Rei's status as a vessel for the soul of [[Lilith]] exempts her from the ordinary rules of synchronization. This would be analogeous to Kaworu, who is a vessel for the soul of [[Adam]], synchronizing with Eva-02 during episode 24 without it's core being reconfigured. Kaworu pilots Eva-02 while not even in the Entry Plug later in the same episodeOthers have suggested that Rei had "projected" an impression of her own soul into the core in order to synch, and this is what Shinji encounters in Ep. 14.


====Counter-argument====
However, Ritsuko seems clear in Episode 23 that an Evangelion ''requires'' a human soul to function, and she said that each Eva contains a human soul.  Also, the Evas came from Adam, not from Lilith.


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 with discerning fans for several reasons:
Proponents of the No Soul theory occasionally object that Both Rei 1 and Naoko were dead, so neither of their souls could have been used.  However, it is well established in the series that souls can be salvaged out of dead bodies and placed in new vessels.  Rei 2's soul was transferred to Rei 3 the same day that the former died; After Kaworu's death, his soul was transferred to the Adam embryo in Gendo's hand, only to be absorbed by Rei 3 along with the hand in EOE.


*It doesn't really answer the basic question of ''why'', out of all people, Gendo (and possibly Ritsuko) would use the soul of Naoko Akagi in Eva Unit 00.
===Naoko Akagi?===
*It doesn't really address the vision of Rei that Shinji had in Eva Unit-00.
[[Image:21 C136 naoko.jpg|right|200px|thumb|Doctor Naoko Akagi.]]
*Naoko was already dead if they wanted to use her soul: after strangling Rei I she committed suicide by throwing herself off the upper level of the command center, landing on one of her own Magi supercomputers.
**The series implies that Naoko kills herself but does not actually show it on-screen. Some have suggested that Gendo actually had Naoko killed off-screen, but there is nothing to actually support this.  Further, in the [[Neon Genesis Evangelion (manga)|manga adaptation]] of the series Naoko is explicitly shown to have killed herself, though the manga is ''not'' set in the same continuity as the series; still, all points seem to agree that Naoko indeed killed herself as was implied.


===Rei 1?===
At one time this was the most pervasive theory:  the soul in Eva-00 is actually that of [[Gehirn]]'s chief computer engineer, Ritsuko's mother, Dr. [[Naoko Akagi]].  The basis for this theory was that the people standing directly behind the glass in the control room when Eva-00 punches it -- Gendo and Rei -- are people for whom Naoko Akagi had a deep personal hatred. Gendo fooled Naoko into thinking he loved her, but was really only using her (as revealed in by Rei I in [[Episode 21]]).  In a fit of rage, Naoko strangled Rei I to death, seeing her as Yui (whom she very strongly resembled) and as "competition" for Gendo's affections. Naoko had good reason to lash out at Gendo himself, even more than Rei, because he had used her. 


The theory which has become more established is that the soul of Eva Unit-00 is the soul of
This, however, is refuted by Ritsuko's knowledge that she was Eva-00's actual targetBut could Naoko actually been after Ritsuko? Actually, Ritsuko got along well with her mother professionally, and they seemed to be on good speaking terms in the flashbacks from Episode 21, but more than once in the series (specifically [[Episode 13]]) Ritsuko reveals that they had a tumultuous personal relationship.  In the series' present, Ritsuko was carrying on an illicit relationship with Gendo just as her mother had been, and Naoko might have seen 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, '''IF''' the soul were Naoko's this '''could''' be interpreted as a reason to attack Ritsuko, however...
"Rei 1"That is, there have been three clones of "Rei Ayanami": Rei 1 (the first one, killed by Naoko Akagi), Rei 2 (who Shinji met in the first episode and dies self-destructing Unit 00 in [[Episode 23]]), and Rei 3 (who appears from the second half of Episode 23 through the remainder of the series and ''The End of Evangelion'').


The obvious hurdle this runs into is that "Rei II" is still alive and well, interacting with Shinji and Asuka in Tokyo-3, and surely she must be "using" her soulHowever, an explanation is offered with the case of Asuka's mother, [[Kyoko Zeppelin Soryu]].  The soul of Shinji's mother Yui Ikari was completely absorbed into Eva Unit 01.  With Kyoko, on the other hand, only a ''fraction'' of her soul was absorbed in the "contact experiment" with Eva 02The portion of Kyoko's soul containing her maternal aspects was absorbed by Eva Unit 02, thus Kyoko was still alive and conscious...albeit, the process of having the portion of her soul containing the aspects of her personality as a mother removed drove her clinically insane.  Still, Kyoko established that ''part'' of someone's soul can be absorbed by an Eva and they can still survive.
Nothing in this speculation explains why Gendo (and possibly Ritsuko) would use the soul of Naoko Akagi in Eva-00 in the first placeAs she views Rei as a rival, and even went so far as to kill Rei's first incarnation, Naoko would be the absolute ''worst'' choice for a compatible soul.  Although it would explain why Eva-00 seems to try to kill Rei 2 in Episode 14, if you ignore Ritsuko's statement that she (Ritsuko herself) was the target, it gives no explanation at all why Rei was even able to synchronize with her. It also  gives no explanation for the vision of Rei that Shinji had in Eva-00.


Thus, the theory runs that after Rei 1 died, a ''portion'' of her soul was placed inside of Eva Unit 00, with the rest being reembodied in the next Rei Ayanami clone, "Rei 2".  Coincidentally, this might explain why Rei 2's behavior seems detached and withdrawn from the world:  just as Kyoko went clinically insane after having part of her soul separated from her body, having a portion of Rei's soul separated to put in Eva 00 might have drastically affected her personalityWe do not see enough of Rei 1's personality to accurately gauge this, though (in the literally one scene in which Rei 1 actually talked, she wasn't running around laughing, etc.)
Naoko proponents also occasionally distort the "mother in the Eva" rule by claiming that Yui, Kyoko, and Naoko were all mothers, completely missing the point that Naoko is not ''Rei's'' mother and that Naoko, like Yui, would be capable of refusing to synch with an unwanted pilot like Yui did in Episode 19 with Rei and the Dummy PlugThe only reason for using Naoko would be if Ritsuko was going to pilot, and she is the wrong age.


This would explain why Shinji sees a "vision" of "Rei" in Eva Unit 00; because the soul inside ''is'' Rei's, or at least a portion of itBut the segment of Rei's original soul (from Rei 1) has branched off a bit from that remaining in Rei II, because they are separated:  "Rei 1" (operating on a fraction of a soul in Eva 00) might be resentful that she was killed.
==The Prevailing Theory==
===Rei 1===
[[File:21 gendo grin 9.jpg|thumb|right|Rei 1 first appears.]]
The theory which has become more established is that the soul of Eva-00 is the soul of "Rei 1"There have been three iterations of "Rei Ayanami":  Rei 1 (the first one, killed by Naoko Akagi), Rei 2 (whom Shinji met in the first episode and who dies self-destructing Eva-00 in [[Episode 23]]), and Rei 3 (who appears from the second half of Episode 23 through the remainder of the series and ''The End of Evangelion'').


This would actually also fit nicely with the list of people that Eva Unit 00 attacked: Rei 1 would want to hurt Gendo because he used her, and Ritsuko as well, because she is upset that she is dead and that her soul has been trapped inside of an Eva Unit by Gendo and RitsukoAlso, killing Ritsuko might indirectly be seen as taking "revenge" on Naoko by killing her daughter.  Rei 1 might hate Rei 2, because Rei 2 replaced her and gets to be alive while she is effectively dead.  In Episode 14, Misato thought that Eva 00 was trying to kill Rei while Ritsuko thought it was trying to kill herselfRitsuko actually knows whose soul is in Eva 00, Misato does not.  Still, both Ritsuko and Rei II would be potential targets of Eva 00 of the soul inside was Rei 1.   
Some people have objected on the grounds that it is well established that all three Reis have Lilith's soul. Rei 2 is still alive and well, interacting with Shinji and Asuka in Tokyo-3, so how could her soul also be in Eva-00?  This is explanained by the case of Asuka's mother, [[Kyoko Zeppelin Soryu]]While Shinji's mother, Yui Ikari, completely absorbed, body and soul, into Eva-01, only the portion of Kyoko's soul containing her maternal aspects was absorbed in the [[Contact Experiment|contact experiment]] with Eva-02Thus Kyoko was still alive and conscious, although the process of having part of her soul sucked out of her drove her clinically insane.  Still, Kyoko established that one can lose part of one's soul and survive.   


A result of this theory is that after Eva Unit 00 self-destructed, along with killing Rei 2, when Rei 3 was created she possessed her ''entire'', reunited soul: this accounts for the difference in behavior between Rei 2 and Rei 3.
Presumably, an indeterminate period of time after Rei 1 died, a portion of her soul was placed inside of Eva-00, with the rest being reembodied in the next Rei Ayanami clone, Rei 2.  This may explain why Rei 2's behavior seems detached and withdrawn from the world; just as Kyoko went clinically insane after having part of her soul separated from her body, having a portion of Rei's soul separated to put in Eva-00 might have drastically affected her personality, although it did not affect her to the extent of driving her insane. If anything, it's the portion in Eva-00 that seems unbalanced.


Rei 2's comment in Episode 23 that "is this the me inside the Eva?" seems to also support the theory that ''another'' "Rei", Rei 1, was the soul inside of Eva 00, and also to imply that Rei 2 was aware of this.  The line, though, does seem to be somewhat open to interpretation (Rei has been known to talk in the third person like that, as in Episode 14, though arguably Rei 2 might have been referring to Rei 1 inside of Eva 00 in that episode).   
This explains why Shinji sees a vision of Rei in Eva-00; because the soul inside ''is'' a portion of Rei's soul.  But the segment of Rei's original soul (from Rei 1) has branched off a bit from that remaining in Rei 2, because they are separated.   


Also, it must be remembered that "Rei's soul", is really "the soul of Lilith", which is being contained in the vessel of Rei's physical body (a clone of Yui Ikari's body). The idea of the "mutual compatibility experiment" in episode 14 also backs up this idea. Why would they even begin to test if Shinji was compatible with Unit-00 and Rei was compatible with Unit-01? This only makes sense if part of Rei/Lilith's soul is in Unit-00. Otherwise, there would be no reason to think Shinji could synch with Unit-00. This is another example of the Rei/Yui/Lilith motif in action, where Rei representing Yui and Lilith could synch with Unit-01 that contains Yui's soul, as well as Unit-00 which contains Lilith's soul. Shinji can synch with Unit-01 obviously because of Yui's soul, but it makes no sense that he could synch with Unit-00 were it not for the presence of Lilith's soul.  
Some people have objected that the Rei which Shinji sees in Eva-00 looks like more like Rei 2, who appears as a teenager, than Rei 1, who died when she was still a small child.  Other's disagree and see Rei 1. The, "it's a teenager" believers say this implies that Shinji is seeing an "imprint" (see the "no soul" theory, above) left by Rei 2 in Eva-00, and not the soul of Rei 1. However, as stated above, when this Rei reappears in Ep. 25, the script explicitly identifies this Rei to be Rei 1.  


====Counter-argument====
This brings us to Eva-00's behavior during the berserk incidents.  Rei 1 might be resentful that she was killed.  Rei 1 has motives to strike out at the same people Eva-00 attacked.  She may want to hurt Gendo because he had her imprisoned in Eva-00.  Her attempt to Kill Ritsuko in Ep. 14 can be seen as taking revenge upon Naoko either by killing her daughter or else she believes she is attacking Naoko herself.  Her seeing Ritsuko with her natural dark hair could be read either way; she recognizes the connection to Naoko, or she is mistaking her for NaokoIn Episode 14, Ritsuko knew she was the target.  Ritsuko is in a position to know whose soul was inside the Eva.
The "Unit 00's soul is Rei 1" theory is actually fairly strong, with few weak spotsHowever there are a few points that the Naoko-camp brings up:


*Rei I was just as dead as Naoko was, so "Naoko is dead" doesn't serve as an effective counter-argument to the Naoko-theory, because it also applies to Rei 1.
In Episode 23, Rei 2 directly confirms Rei 1's presence inside the Eva with the question, "Is this me ? The me inside the Eva?". It's also been suggested that after Eva-00 self-destructed and Rei 3 was created, as both portions of her soul were now available, she would have possessed her entire reunited soul.  But as the only evidence cited is the difference in behavior between Rei 2 and Rei 3 this should be treated as theoryIt could also be explained by any number of things such as resentment over being forced back to life. Rei 3's personality also appears much closer to Rei 2's than what is known of Rei 1's.  
**Thus, if either Naoko Akagi ''or'' Rei 1's soul was used in Eva 00, Gendo would have had to get a soul from someone who was already deadHowever, the science which the transfer and manipulation of souls in the series is based on, the nebulously defined "[[Metaphysical Biology]]", can be seen to effectively serve as a "magic wand" explanation in this regard:  they have developed a branch of science which can actually manipulate souls, even from bodies which have died.  Rei's soul was transfered from Rei 1 to Rei 2 only after Naoko strangled her to death, and Rei 2's soul was transfered to Rei 3 only after Rei 2 died fighting ArmisaelAlso, [[Kaworu Nagisa|Kaworu's]] soul was salvaged into the Adam embryo after his death at the hands of Shinji and Unit-01.
*The Naoko-argument also points out that Naoko was a mother, and Yui and Kyoko were also mothers, but Rei 1 was not a mother.  However, the point seems to ''not'' be simply that someone is a mother, but that they are the mother ''of the actual pilot'', so this really isn't a strong counterpoint. (In an [http://eva.onegeek.org/pipermail/evangelion/2006-November/003855.html interview with Sadamoto in ''Der Mond''], Sadamoto outright says "the dead mother is inside the robot, which is operated by mental/psychical bonding with the child").
*The last point brought up against the Rei I theory is that the vision of Rei which Shinji sees looks like Rei 2, who is a teenager, when Rei I died when she was still a small child, which would imply that Shinji is seeing an "imprint" left by Rei 2 in Eva 00, and not the soul of Rei 1.


Of course, a dreaded but non-ignorable possibility is that '''the writers might have changed their minds about the identity of the soul in Eva 00 between Episode 05 and subsequent episodes'''. The writing team on ''Evangelion'' is known to have greatly changed several of their original ideas for the show between when its beginning and the later episodes of the series which shifted to a drastically dark tone. Hints established in an early episode like Episode 05, i.e. Eva 00 attacking a window Gendo is standing behind, and Ritsuko hinting at the identity of Eva 00's soul, might have been meant to hint that someone else was ''originally'' meant to be the soul in Eva 00, but that this was later switched to be someone else, which hints from later episodes point to.
Finally, the idea of the "mutual compatibility experiment" in Episode 14 has been cited as confirmation of this theory. The intention of the experiment was to see if Shinji was compatible with Eva-00 and Rei with Eva-01, with any idea of compatibility with Eva-02 being dismissed.<ref>The dismissal of compatibility with Eva-02 is interesting in hindsight, because Shinji broke his synch records during his one mission inside Eva-02 in [[Episode 08]], and even if Asuka was in the entry plug with him it is quite specific that ''both'' of them synced with the Eva, making it almost explicit that Shinji is compatible with Eva-02. So while there may have been no need to test Shinji in Eva-02 due to having all the synchronization data that they needed, it would logically be necessary to test Rei's compatibility with Eva-02 prior to installing the Dummy Plug. Dialog between Gendo and Ritsuko in [[Episode 18]] states that the Dummy Plug (with Rei's data in it) was installed in both Eva-01 and Eva-02, which would make no sense if Rei wasn't compatible with Eva-02 at some level. </ref> Because Rei is connected with both Yui and Lilith (herself) she should be able to synch with either Eva-00 or Eva-01, however it is much less certain why they would think that Shinji had any connection with Rei 1 that would allow him to synch with Eva-00, or what the purpose of such a potentially dangerous test would be in light of the previous berserk incident.


==Conclusion==
==Conclusion==
The Rei 1 theory has become the prevailing theory due to the number of people who view it as the stronger case.  This is why other theories, such as the "Naoko" theory and the "No Soul" theory have faded, but not vanished over time.
==Addendum:  Recently Proposed Theories==


'''The exact identity of the soul in Evangelion Unit-00 remains without an ''utterly definitive'' answer; nonetheless it was ''probably'' Rei I's soul''', which was itself a fragment of Rei's soul (being actually the soul of Lilith).   
===Unit-00's Soul is an Unknown Fragment of Lilith's Soul===
It has recently been suggested a fragment of Lilith's soul was seperated for the specific purpose of becoming Unit-00's soul.  This theory has not undergone all the debate and vetting the other theories received, thus it in uncertain how the fan community will receive itAt least two objections have already been raised.


Eva 00 ''had'' a soul, and based on Ritsuko's reaction in Episode 05, it was probably someone of significance in the storyline as opposed to just a random person's.
*The soul looks like Rei.  The Evangelion philosophy of existence states that we are defined by our relations with others.<ref>Rei states this about herself in Ep. 25.</ref>  Thus Lilith turns into Rei after their reunion in EOE.  During her time as a human Lilith has effectively ''become'' Rei.  But why would a soul fragment that had never been Rei look like Rei?  Unless the very act of synching can alter a soul's appearance, Unit-00's soul must have spent some time as a Rei soul.


The theory that it was Naoko Akagi's soul does not really hold up well under scrutiny; yes, those targeted by the berserk Unit 00 were enemies of Naoko Akagi, but they were also enemies of Rei I.   
*A Lilith soul fragment wouldn't have as strong a motivation to go berserk and attack the other characters as Rei 1 or even Naoko (e.g. no revenge for her her own murder, or jealous rages.  The motive would likely be simple resentment over being imprisoned in Unit-00.   


Ultimately, the series left it vague enough that if in a future incarnation of ''Evangelion'', series creator [[Hideaki Anno]] himself reveals the soul of Eva Unit 00 was actually meant to be the soul of Naoko Akagi, yes, it would be one step above "just making it up out of thin air", and two steps above "midichlorians".
As this theory is relatively recent it's status here is uncertain.  After a more thorough debate and discussion, a consensus will be reached on whether this secton should be expanded, deleted, or left as is.


Nonetheless, just because Naoko Akagi ''happens to fit'' some of the evidence doesn't mean she was meant to be the soul of Eva 00:  indeed, at no point in the series is it actually ''implied'' that Naoko was the soul in Eva 00.  It is in all probability just a coincidence that people Naoko would want to take revenge on, happen to also be people that Rei I would want to take revenge on.
==References==
{{reflist}}


[[Category:A to Z]]
[[Category:A to Z]]
[[Category:Theory and Analysis]]
[[Category:Theory and Analysis]]

Latest revision as of 04:32, 22 May 2021

Ritsuko reveals in Episode 23 that, necessary to function, all Evangelions contain a human soul, and it is heavily implied throughout the series and explicitly stated in the Classified Information that that soul must be the pilot's mother. Eva-01 contains the soul of Shinji's mother Yui Ikari, and Eva-02 contains at least 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, likewise, that Toji Suzuhara's mother is dead. Thus, when Toji becomes the pilot of Eva-03, it is implied that it contains his mother's soul. However, Rei was created from the Angel Lilith and the remains of Yui Ikari, and thus does not have a mother. The identity of the soul contained within Eva-00's core is never directly stated in the series, however, evidence and clues as to the identity of the soul in Eva-00 appear several times during the series, particularly in Episode 05, Episode 14, Episode 23 and Episode 25 and also Episode 24.

The Evidence

Rei's Eva-00 was the first working Prototype out of a very long string of failures; it goes out of control twice and is "buggy", often returning errors when under testing. As stated above, Rei has no mother, so unlike Shinji and Asuka, her mother's soul cannot be in her Eva. Aside from the construction defects, the soul inside Eva-00 not being Rei's mother is the likely explanation as to why Rei's Eva does not always function properly.

Episode 5

During a startup test, Eva-00 goes berserk.

Unit-00 punches the window.
  • While berserk, Eva-00 repeatedly punches a glass window behind which Gendo Ikari is standing. Ritsuko is further behind the glass but in plain sight of the Eva.
  • Eva-00 rejects 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-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: No. That can't be it.

Episode 14

Distorted Rei seen by Shinji inside Eva-00. (Click to see animation.)

A unit interchangeability test is conducted to see if Shinji can synchronize with Eva-00 and if Rei can synchronise with Eva-01 so Nerv can implement their plan for the Dummy Plug. During this test Eva-00 goes berserk.

  • As soon as Shinji is connected via the A-10 nerve to Eva-00 he sees a rapid burst of images of Rei. Shinji says:
Shinji: What is this? Something's trying to get directly into my brain. Ayanami? Rei Ayanami? This impression is Rei Ayanami, isn't it? Ayanami? Isn't it her?

When this Rei reappears in Ep. 25, she is explicitly identified in the script as Rei 1.

  • Eva-00 goes berserk, and repeatedly punches a glass window behind which Rei is standing. Misato speculates "could it be that Unit-00 just tried to kill Rei?", but after Misato finishes talking to Ritsuko, Ritsuko thinks to herself: "The person Unit-00 wanted to hit was me. I'm sure of it." Ritsuko is in a position to know what soul is where; Misato is not.
  • Eva-00 seems to mistake Ritsuko for her mother Naoko; In the "Eva point-of-view" shots Eva-00 sees Ritsuko with Naoko's dark hair. It is unlikely that this is just an animation error because the other details of Ritsuko's appearance and clothing are accurate, such as her unbuttoned lab coat and blue shirt.
Possible Eva-00 targets.
Observe Ritsuko's hair color.
Note the details in both images. Blue shirt, open lab coat.


Episode 23

Armisael speaks with Rei during Episode 23.
  • The Angel Armisael begins to merge with Eva-00 and makes direct contact with Rei's mind. When Rei first feels Armisael contacting her mind, she thinks to herself: "Who's there? Me? The me inside the Eva? No, I can sense that there's someone other than me." This reinforces the evidence from Ep. 14 that Eva-00's soul is somehow connected to Rei.

Episode 24

  • This episode is important for our understanding of the synchronisation process between Rei and Eva-00. Kaworu is the only other example of a Seed of Life's soul present in a Lilin vessel besides Rei who pilots an Eva. Kaworu synchronises with Eva-02 without its core being reconfigured and later pilots Eva-02 while not present in the Entry Plug. The reason for this is that Kaworu is made of the same matter as Eva-02.
I don't need no entry plug!
Kaworu: The Eva are made of the same body as I am. Because I am born from Adam as well. I could merge with them, if only they didn't have souls. Unit-02's soul has shut itself away for now.
  • Rei is made of the same matter as Eva-01 which was grown from Lilith, but not Eva-00. This suggests that Rei successfully synched with Eva-01 in Ep. 14 only because Yui allowed it. Yui has not shut herself away, and successfully rejects synching with Rei in Ep. 19.

Episode 25

The wide-eyed Rei in Episode 25.
  • During Rei's experience of Instrumentality she sees a vision of the same wide-eyed "Rei" that Shinji saw in episode 14 when he was in Eva-00. The script for episode 25 explicitly identifies this Rei as Rei 1.

Supplemental evidence

"A unit called a core is used to eliminate the discrepancies in Eva, a human being with the body of a god and a soul. The soul of the pilot's mother, which is placed within the core, acts as a medium and makes piloting possible... Due to difficulties encountered in the development of Eva-00, the core's system is poorly constructed, and she falls behind in performance capacity as a result. Another reason for her inferiority is that Eva-00's pilot, Rei, does not have a mother."

Also, in an interview with Sadamoto in Der Mond, Sadamoto outright says "the dead mother is inside the robot, which is operated by mental/psychical bonding with the child").

Rei 1 speaking with Rei 2 during the Leliel battle.
  • In the actual Neon Genesis Evangelion 2 PSP port video game (which Anno also worked on), when whichever pilot being played as is about to break free from Leliel, the soul of the Eva contacts the pilot. In the case of Shinji, Asuka, and Toji, they see their mothers, while Kaworu is able to force Eva-04 out of Leliel. However, Rei 2 sees the distorted Rei visage shown in Episode 14 (considered to be a hint of Rei 1 being inside Eva-00) and Episode 25 and is designed with "????" as she speaks to Rei.
Rei 1 designated as ???, tells Rei 2 that she must "Retrieve the Fruit of Life from Adam" during the Leliel battle.

Analysis

Eva-00 could have been aiming for Gendo Ikari, Ritsuko Akagi, or its own pilot Rei Ayanami, during either berserk incident. Based on Ritsuko's comment as she trailed off in Episode 05, Ritsuko knows more about the situation than she is telling Misato and there is something of importance which she considers before dismissing as impossible. As Nerv's head scientist, Ritsuko must herself know whose soul is in Eva-00, and she herself stated that all Evas have a human soul inside them. She knows that Rei is just one of a series of clones and possibly knows about the fate of Rei 1 as well.

Eva-00 also seemed to violently reject Shinji, although this may not have been because of Shinji specifically, but rather because someone other than her normal pilot was trying to synch with her. Shinji sees an "impression" of what he thinks is Rei while synchronized with Eva-00, but ends by saying "...isn't it her?", hinting that the "impression" he sees isn't the "Rei" he knows. Rei similarly speaks of "the me inside the Eva".

What does all this mean? There have been many theories over time, but of the three most popular, two have generally fallen into disfavor after many years of sometimes contentious debate. We will address those two first.

Formerly Popular Theories

Eva-00 Has no Soul?

It has been theorized that Eva-00 simply has no soul at all, and that Rei's status as a vessel for the soul of Lilith exempts her from the ordinary rules of synchronization. This would be analogeous to Kaworu, who is a vessel for the soul of Adam, synchronizing with Eva-02 during episode 24 without it's core being reconfigured. Kaworu pilots Eva-02 while not even in the Entry Plug later in the same episode. Others have suggested that Rei had "projected" an impression of her own soul into the core in order to synch, and this is what Shinji encounters in Ep. 14.

However, Ritsuko seems clear in Episode 23 that an Evangelion requires a human soul to function, and she said that each Eva contains a human soul. Also, the Evas came from Adam, not from Lilith.

Proponents of the No Soul theory occasionally object that Both Rei 1 and Naoko were dead, so neither of their souls could have been used. However, it is well established in the series that souls can be salvaged out of dead bodies and placed in new vessels. Rei 2's soul was transferred to Rei 3 the same day that the former died; After Kaworu's death, his soul was transferred to the Adam embryo in Gendo's hand, only to be absorbed by Rei 3 along with the hand in EOE.

Naoko Akagi?

Doctor Naoko Akagi.

At one time this was the most pervasive theory: the soul in Eva-00 is actually that of Gehirn's chief computer engineer, Ritsuko's mother, Dr. Naoko Akagi. The basis for this theory was that the people standing directly behind the glass in the control room when Eva-00 punches it -- Gendo and Rei -- are people for whom Naoko Akagi had a deep personal hatred. Gendo fooled Naoko into thinking he loved her, but was really only using her (as revealed in by Rei I in Episode 21). In a fit of rage, Naoko strangled Rei I to death, seeing her as Yui (whom she very strongly resembled) and as "competition" for Gendo's affections. Naoko had good reason to lash out at Gendo himself, even more than Rei, because he had used her.

This, however, is refuted by Ritsuko's knowledge that she was Eva-00's actual target. But could Naoko actually been after Ritsuko? Actually, Ritsuko got along well with her mother professionally, and they seemed to be on good speaking terms in the flashbacks from Episode 21, but more than once in the series (specifically Episode 13) Ritsuko reveals that they had a tumultuous personal relationship. In the series' present, Ritsuko was carrying on an illicit relationship with Gendo just as her mother had been, and Naoko might have seen 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, IF the soul were Naoko's this could be interpreted as a reason to attack Ritsuko, however...

Nothing in this speculation explains why Gendo (and possibly Ritsuko) would use the soul of Naoko Akagi in Eva-00 in the first place. As she views Rei as a rival, and even went so far as to kill Rei's first incarnation, Naoko would be the absolute worst choice for a compatible soul. Although it would explain why Eva-00 seems to try to kill Rei 2 in Episode 14, if you ignore Ritsuko's statement that she (Ritsuko herself) was the target, it gives no explanation at all why Rei was even able to synchronize with her. It also gives no explanation for the vision of Rei that Shinji had in Eva-00.

Naoko proponents also occasionally distort the "mother in the Eva" rule by claiming that Yui, Kyoko, and Naoko were all mothers, completely missing the point that Naoko is not Rei's mother and that Naoko, like Yui, would be capable of refusing to synch with an unwanted pilot like Yui did in Episode 19 with Rei and the Dummy Plug. The only reason for using Naoko would be if Ritsuko was going to pilot, and she is the wrong age.

The Prevailing Theory

Rei 1

Rei 1 first appears.

The theory which has become more established is that the soul of Eva-00 is the soul of "Rei 1". There have been three iterations of "Rei Ayanami": Rei 1 (the first one, killed by Naoko Akagi), Rei 2 (whom Shinji met in the first episode and who dies self-destructing Eva-00 in Episode 23), and Rei 3 (who appears from the second half of Episode 23 through the remainder of the series and The End of Evangelion).

Some people have objected on the grounds that it is well established that all three Reis have Lilith's soul. Rei 2 is still alive and well, interacting with Shinji and Asuka in Tokyo-3, so how could her soul also be in Eva-00? This is explanained by the case of Asuka's mother, Kyoko Zeppelin Soryu. While Shinji's mother, Yui Ikari, completely absorbed, body and soul, into Eva-01, only the portion of Kyoko's soul containing her maternal aspects was absorbed in the contact experiment with Eva-02. Thus Kyoko was still alive and conscious, although the process of having part of her soul sucked out of her drove her clinically insane. Still, Kyoko established that one can lose part of one's soul and survive.

Presumably, an indeterminate period of time after Rei 1 died, a portion of her soul was placed inside of Eva-00, with the rest being reembodied in the next Rei Ayanami clone, Rei 2. This may explain why Rei 2's behavior seems detached and withdrawn from the world; just as Kyoko went clinically insane after having part of her soul separated from her body, having a portion of Rei's soul separated to put in Eva-00 might have drastically affected her personality, although it did not affect her to the extent of driving her insane. If anything, it's the portion in Eva-00 that seems unbalanced.

This explains why Shinji sees a vision of Rei in Eva-00; because the soul inside is a portion of Rei's soul. But the segment of Rei's original soul (from Rei 1) has branched off a bit from that remaining in Rei 2, because they are separated.

Some people have objected that the Rei which Shinji sees in Eva-00 looks like more like Rei 2, who appears as a teenager, than Rei 1, who died when she was still a small child. Other's disagree and see Rei 1. The, "it's a teenager" believers say this implies that Shinji is seeing an "imprint" (see the "no soul" theory, above) left by Rei 2 in Eva-00, and not the soul of Rei 1. However, as stated above, when this Rei reappears in Ep. 25, the script explicitly identifies this Rei to be Rei 1.

This brings us to Eva-00's behavior during the berserk incidents. Rei 1 might be resentful that she was killed. Rei 1 has motives to strike out at the same people Eva-00 attacked. She may want to hurt Gendo because he had her imprisoned in Eva-00. Her attempt to Kill Ritsuko in Ep. 14 can be seen as taking revenge upon Naoko either by killing her daughter or else she believes she is attacking Naoko herself. Her seeing Ritsuko with her natural dark hair could be read either way; she recognizes the connection to Naoko, or she is mistaking her for Naoko. In Episode 14, Ritsuko knew she was the target. Ritsuko is in a position to know whose soul was inside the Eva.

In Episode 23, Rei 2 directly confirms Rei 1's presence inside the Eva with the question, "Is this me ? The me inside the Eva?". It's also been suggested that after Eva-00 self-destructed and Rei 3 was created, as both portions of her soul were now available, she would have possessed her entire reunited soul. But as the only evidence cited is the difference in behavior between Rei 2 and Rei 3 this should be treated as theory. It could also be explained by any number of things such as resentment over being forced back to life. Rei 3's personality also appears much closer to Rei 2's than what is known of Rei 1's.

Finally, the idea of the "mutual compatibility experiment" in Episode 14 has been cited as confirmation of this theory. The intention of the experiment was to see if Shinji was compatible with Eva-00 and Rei with Eva-01, with any idea of compatibility with Eva-02 being dismissed.[1] Because Rei is connected with both Yui and Lilith (herself) she should be able to synch with either Eva-00 or Eva-01, however it is much less certain why they would think that Shinji had any connection with Rei 1 that would allow him to synch with Eva-00, or what the purpose of such a potentially dangerous test would be in light of the previous berserk incident.

Conclusion

The Rei 1 theory has become the prevailing theory due to the number of people who view it as the stronger case. This is why other theories, such as the "Naoko" theory and the "No Soul" theory have faded, but not vanished over time.

Addendum: Recently Proposed Theories

Unit-00's Soul is an Unknown Fragment of Lilith's Soul

It has recently been suggested a fragment of Lilith's soul was seperated for the specific purpose of becoming Unit-00's soul. This theory has not undergone all the debate and vetting the other theories received, thus it in uncertain how the fan community will receive it. At least two objections have already been raised.

  • The soul looks like Rei. The Evangelion philosophy of existence states that we are defined by our relations with others.[2] Thus Lilith turns into Rei after their reunion in EOE. During her time as a human Lilith has effectively become Rei. But why would a soul fragment that had never been Rei look like Rei? Unless the very act of synching can alter a soul's appearance, Unit-00's soul must have spent some time as a Rei soul.
  • A Lilith soul fragment wouldn't have as strong a motivation to go berserk and attack the other characters as Rei 1 or even Naoko (e.g. no revenge for her her own murder, or jealous rages. The motive would likely be simple resentment over being imprisoned in Unit-00.

As this theory is relatively recent it's status here is uncertain. After a more thorough debate and discussion, a consensus will be reached on whether this secton should be expanded, deleted, or left as is.

References

  1. The dismissal of compatibility with Eva-02 is interesting in hindsight, because Shinji broke his synch records during his one mission inside Eva-02 in Episode 08, and even if Asuka was in the entry plug with him it is quite specific that both of them synced with the Eva, making it almost explicit that Shinji is compatible with Eva-02. So while there may have been no need to test Shinji in Eva-02 due to having all the synchronization data that they needed, it would logically be necessary to test Rei's compatibility with Eva-02 prior to installing the Dummy Plug. Dialog between Gendo and Ritsuko in Episode 18 states that the Dummy Plug (with Rei's data in it) was installed in both Eva-01 and Eva-02, which would make no sense if Rei wasn't compatible with Eva-02 at some level.
  2. Rei states this about herself in Ep. 25.