Dogen gives Jack a pill to give to Sayid, which he later confesses is to get rid of the "darkness" and is actually poison. When Ben and the Others used a poison gas attack on the Dharma compound during The Purge, they were actually preventing the "darkness" from spreading to the rest of the island, as the "darkness" had already claimed the Dharma encampment.
Also, Daniel and Charlotte prevented a large amount of poison gas from being released by Ben at The Tempest. Perhaps Ben had anticipated that the "darkness" had already spread to some of the inhabitants of the island or had been carried over by the science team.
The reference to being 'infected' was suggested to be an imperfect translation of Dogen's words in Japanese. Perhaps the Darkness is some sort of inside knowledge about the island that gradually manifests itself within the person's mind causing them to act "strangely." Once this knowledge is revealed to the audience, the behavior of those that are "infected" will not seem so strange. For example, the behavior of the Others in Seasons 1 and 2 seemed very "strange" to the audience, but to them it was perfectly rational once their backstory was (slowly) uncovered.
Would the pill have killed Sayid? If so, then why didn't Dogen just order his people to shoot Sayid instead of going to all the trouble? Perhaps the pill would have cured Sayid, but would kill a non-infected person.
To be "infected" you have to first die. After this your body can be "claimed." Shooting such a revived entity is perhaps pointless?
Claire was infected, but was not killed.
The Others are subject to the same "rules" that prevent Ben and Widmore and Jacob and MIB from killing each other directly. Sayid is now on the other "side" so they can't kill him. They need Jack to get him to swallow the pill, just as MIB as Locke needed to get Ben to kill Jacob.
Robert was exhibiting behaviour of what we would consider the 'infected', yet Danielle was able to kill him with a gunshot.
It's possible that pill is not poison to Sayid. It could be some sort of "cleansing agent." If Dogen believes that Sayid is "infected by MIB" although he never says that he is but clearly implies it, the pill could cleanse him from MIB. They clearly say if Sayid dies that they would be in trouble, so why would Dogen deliberately kill him? It makes no sense. He tells Jack it's poison because if Jack were to take it, he would be cleansed of Jacob's blessings. Out there, but a possibility.
The pill is chemo for the claimed.
They didn't want Sayid to die because if Sayid died under the certain circumstances of his death he would be claimed by MIB. Sayid died. Sayid is now claimed by MIB. Sayid is now an enemy of the Others.
Is there any evidence that the "darkness" is the same as MIB? If MIB could "claim" the bodies of the dead, why didn't he do this with the real Locke's body, instead of merely imitating Locke and leaving the real body alone?
When people are reborn on the island, they belong to one of two camps (such as Jacob's or the MIB's) based on how they died or who is responsible for their deaths. This is why Dogen repeatedly asks about who is responsible for Sayid's bullet wound. When Sayid is reborn, they conduct a test that reveals him to be part of the enemy camp. This is because Sayid died in an effort to change history and fight fate. They ask him to ingest a poison voluntarily because this sort of willful display of faith would change the circumstances of his death and give him an opportunity for a rebirth into their own camp.
The pill is not directly a poison. If it were they wouldn't need Sayid to take it willingly, they would have forced him to take it during the torture. The pill most likely is something that will help Sayid, but harm people who have not been infected/"claimed."
The "Darkness" is actually the "sickness" that affected Rousseau's team.
Something in the water?
Dogen and Lennon noted that the spring in the Temple was cloudy, not clear like it normally was. When Sayid was put in the spring and died instead of being healed, he came back to life supposedly infected by the "darkness." Perhaps Smokey has contaminated the ground water supply of the island. Jin was about to take a drink from the stream and was abruptly stopped by the Others. Even though it was to find out what happened to Kate, they may have saved him from being contaminated as well.
Recall that Dogen himself placed his cut hand in the water to test its healing powers. If the Others thought the water might be contaminated, Dogen would never have done that.
Smokey is actually the good guy and is trying to protect the losties and defeat Jacob who has continually manipulated situations on this show.
The contrast between clear and murky water is an extension of the white and black symbolism associated with Jacob and his Nemesis.
Now that Jacob is dead, his Nemesis has control over the springs, and therefore was able to "infect" Sayid.
At the end of the episode you can see that Dogen offers boiled water to Jack (tea). Is it that boiling water prevents them from getting infected?
The water became murky immediately after Jacob's death.
First post, bear with me, the hot springs are fed from something deep within the island that both "heats" them and provides the ability to "heal"...something of great "power" on the island. If it turned dark after Jacob died, that would mean they were being powered by something different...MIB. (If this is true, judging by the Others' confusion - asking why it was dark, determining if the water would even heal a cut hand - i'd say this is the first time MIB found his loophole. Otherwise, Dogen certainly would have remembered that the last time it darkened, Jacob was dead, and not be shocked by Hurley's news.) Remember last year when Carlton or JJ said that the volcano was not insignificant and would be explained this season? What if the volcano is powering the springs literally and the whole island metaphorically? It would work towards an explanation of why MIB takes the form of smoke and the significance of the ash (a volcano is also something strong enough to sink an island) and Dharma - who had enough understanding of Smokey to create the sonar fence - were doing geothermal research.
Maybe the Bomb in the X timeline destroyed this source of geothermal heat that intuition says that it would take alot of energy to move alot of earth (amazing how small we are compared to this rock).
Did anyone notice that the murky water from the spring is similar to the water in Ben's chamber that summons the monster? It may be possible MIB has an infection effect on water, also that the monster lives in the chamber and tunnels under the temple. Also the fact that in healing, Richard said Ben would never be the same, it is possible that by healing in the spring it is giving the person's life to the island, hence becoming one of the Others. It's just that Sayid may have been claimed by the monster, or simply been infected by it.
When Jacob was alive the spring was clear, but when he died the water became dark, 'cause of the MIB, and when Sayid was put in the spring when it was dark, he became claimed for the MIB.
Jack Was Tested
Dogen is actually performing two tests. First, Sayid is tested for the Infection. Second, Jack is being tested to be the new leader. Supporting evidence:
Jack is told that Sayid must take the pill willingly. Poison as we know it does not require the victim to take it willingly. The poison Dogen gave Jack will work whether Sayid takes it willingly or whether he is forced. Dogen doesnt really care. He will have Sayid killed with this pill or by some other means. The pill is given to Jack to see if Jack will actually convince a friend to take a pill whose contents he does not understand. This fits with Jack's "flaw" that is explained in the previous seasons. Jack wants to fix everything. Furthermore, he is a surgeon. Fixing Sayid's "infection" with a mystery pill would seem like something Jack would do without question, particularly if it 'redeems' everything he did up to that point. This parallels Jack's statement that "nothing is irreversable" in the alternate timeline. Clearly there are limits to what a neurosurgeon can fix. So Jack's flaw is that he must fix everything, and convincing Sayid to take a pill which Jack himself does not understand would indicate that Jack has not made a break with his past.
Locke was tested in a similar way. Ben and Richard took Locke to some ruins where his father, Anthony Cooper, was tied up. Locke was told that he must kill Cooper to show that he has made a clean break with his past. Truth is, the only way Locke can move on is to accept his condition, accept his past, and forgive his father--which he may have actually done in the alternate timeline (also John seems to have already restored his 'faith' in the alternate timeline when he was talking to Jack about the airline knowing where his father was at). By not killing Cooper at the ruins, John appeared to pass the test. Ben tells John that he shouldnt bother following them unless he has Cooper's corpse. This is not the truth. Ben knows that John must not kill his father to take Leadership of the Others and this is Ben manipulating John so that Ben himself can remain the Leader. John is later responsible for Cooper's death at the hands of Sawyer, so John actually failed the test unknown to Richard who later thinks that John really is the Leader b/c he passed the test at the ruins.
The pill itself is probably poison and not a placebo. When Jack takes the pill, Dogen acts swiftly to force Jack to spit-up the pill. Dogen certainly can't have his Leader dead! However this does show that Dogen intends for Sayid to be dead at some point, but the pill itself is probably just a method chosen to test Jack. He will try to kill Sayid some other way. If Jack becomes the new Leader, this could place Dogen and Jack in conflict in a later episode.
Jacob knew in advance that Dogen and Jack would eventually meet in the future and gave Hurley the guitar case with the note with that knowledge in mind. The note contained instructions to Dogen to "test" Jack to be the new Leader of the others. The note had Jack's name in it, which is why Dogen asked for their names. The note had nothing to do with Sayid's condition. Instead, Dogen/Lennon stated that not saving Sayid would be a bad thing because if Sayid is dead, they cant test Jack with the pill.
When Jack asked why Dogen doesnt speak English, he said that he does it to set him apart from everyone. He then explains that its important for him to be seen as set-apart from the rest so it is easier for those that depend on him to follow his instructions. This almost seems like advice.
Jack's tattoo is translated in the show as "He walks among us, but is not one of us." This is similar to how Dogen explains that he sets himself apart.
Jacob told Hurley he needed to get Sayid to the temple to save his life; however, its reasonable to assume Jacob knew the healing powers of the spring were gone. These instructions were just a ruse to get Jack to the temple.
In The Subsitute, it is revealed by the MIB that the 815 survivors are candidates for being the new 'guardian of the island'. This seems to support the theory that Jack was being tested by Dogen, except instead of being tested to be the new Leader, he's being tested to be the new Jacob.
Same goes for Locke with Anthony Cooper.
Why did Sayid need to voluntarily take the pill, as opposed to just forcing him to take it?
I think it was a bit obvious that they couldn't force Sayid to take the pill because they are not allowed to kill candidates. The pill also had to be taken by Sayid willingly but without him being aware it would kill him since candidates cannot commit suicide.
Since it was implied that candidates can only be killed by other candidates, maybe they just needed some way to convince Jack to do it. It wouldn't really matter if Jack forced Sayid to take it, they just couldn't do it themselves.