The smoke monster is considered by some to be a security system for the Island. The Others summoned it to fend off enemies like the mercenaries from the freighter. Ben and Eko also viewed the smoke monster as a judge, who evaluates the pasts of characters it encounters and decides whether they deserve to live or die. ("The Cost of Living") ("The Shape of Things to Come") ("Some Like It Hoth") Despite this, it may or may not be supposed to exist on the Island at all, having been created when Jacob threw his brother into the Heart after his Mother previously warned against entering it.
What are the motivations of the smoke monster?
The smoke monster was desperate to leave the Island, where he had felt trapped for over 2,000 years. He was willing to stop, or kill, anyone he perceived as a threat to that goal. ("The Substitute") ("Across the Sea")
Why does the monster make mechanical sounds?
They are actually the electrical sounds naturally emanating from the Monster's composition. ("The 23rd Psalm") This is because the Monster was made from the Heart of the Island's electromagnetism. ("Across the Sea") ("The End")
How was the Man in Black able to appear as Christian Shephard to Jack off the Island?
Since the Man in Black wasn't able to leave the Island, Jack's off-Island visions of his father were either psychological--due to substance abuse or simply stress--or psychic in nature. ("Something Nice Back Home")
What was the "it" that killed all the other members from Rousseau's expedition?
Taking into account Rousseau's mental instability, shifting accounts of the story, and position as the actual murderer of her team, it is difficult to determine what she meant when she recorded her messages. However, she likely meant the Black Smoke or the Sickness. ("Solitary") ("This Place Is Death")
How did Montand lose his arm?
He was taken by the Monster to the Temple entrance, where the rest of his team tried to pull him up, though the Monster managed to pull him down, ripping his arm off. ("This Place Is Death")
Jacob's intent for the Others was to prove that people could be good on their own accord. Their primary goal was to protect the island from threats. ("Solitary") ("Ab Aeterno")
Why did they kidnap children?
For the children's own protection, according to Ben. Ben had a particular fondness for children, perhaps due to his own troubled upbringing; his refusal to kill Danielle and his kidnapping Alex against orders divided him and Charles Widmore. More broadly, the Others were unable to give birth on the island, so they kidnapped to supplement their population. They were also intently interested in running tests on some children, such as Walt, who exhibited unusual powers. ("Dead Is Dead")("Raised By Another") ("Not in Portland")
Nothing related the two. The vaccine allegedly prevented a different disease, one from which the Swan was quarantined. This disease did not exist; this hoax helped confine the Swan inhabitants. ("Man of Science, Man of Faith") ("Live Together, Die Alone") The Others also injected Claire with this vaccine, allegedly to protect her from disease, but an implant they inserted, not the Sickness, caused her later symptoms. ("One of Us")
Why are special people inclined towards the Island?
The Island is the source of the Light in all of mankind, circulating "life, death, and rebirth". ("Across the Sea") This suggests that special people have a stronger concentration of the Light and therefore a stronger natural connection to the Island.
What causes certain characters to have these powers?
Equally worth mentioning is that Hurley's destiny towards the Island manifested in a different way before the crash, via the Numbers, which Hurley believed was a curse. ("Numbers") This continued after rescue from the Island. ("There's No Place Like Home, Part 1") However, Jacob told Hurley that he was not cursed, but blessed. ("The Incident") We later learn that the Numbers corresponded to Jacob's candidates to protect the Island. ("The Substitute") ("Lighthouse")
Each number corresponds to the degree Jacob must turn his wheel to view candidates in the lighthouse. Each number was the degree of the remaining 6 candidates for his replacement. They were a sort of filing system, as seen in his cave. ("The Substitute") ("Lighthouse")
Why did the Numbers appear on the Swan hatch and why were they the code for the Hatch computer?
Why did the Numbers reappear regularly both on and off the Island?
The Numbers also represent the factors of the core values of the Valenzetti Equation, which predicts the date of the destruction of mankind. These Numbers correspond to various human and environmental factors, suggesting that they are embedded in the structure of the universe. This is also likely why the Numbers appeared to be cursed. The purpose of the DHARMA Initiative was to alter these values in order to stave off the destruction of mankind. The values were broadcast from the radio tower, with the intent of using the broadcast to determine when DHARMA had succeeded in changed them. ("The Lost Experience")
The frequent appearance of the numbers through out the show also demonstrates apophenia, or human's ability and desperation to see a pattern in the randomness.This relates back to the show's overall them of fate versus free will.
When Frank Lapidus lands the Ajira Flight 316 on the island, there is a Numbers broadcast in the same voice that Rousseau's team heard. If Danielle erased this, where is it coming from?
The Ajira Flight likely received the transmission bouncing through time, as radio waves are known to do on the Island. ("The Long Con")
Why did a bright light suddenly appear when Locke banged the Hatch door?
Because the Hatch occupant, Desmond Hume turned on the light after hearing a noise from outside. ("Live Together, Die Alone")
Why was the inside of the hatch door labeled "quarantine"?
The occupants of the Swan were under the impression that they had to wear a hazmat suit in order to leave the station, thus the quarantine was likely a way to keep them inside the Swan to ensure that the button would be pushed. This quarantine is likely how Radzinsky and Kelvin were able to survive the purge. ("Live Together, Die Alone")
Why were they wearing priest outfits, even though the plane was filled with Virgin Mary statues filled with heroin, and one of the corpses has a gun?
Yemi, the corpse found by Boone on the plane, was an actual Catholic priest, whose help the drug smugglers (Eko, Olu and Goldie) needed. Only foreign and missionary planes were allowed to take off from Nigeria, which prevented the drug smugglers from getting their drugs out of the country to more profitable markets. He helped them only after they threatened to burn down his church, while the other corpse was disguised as a priest in order to claim the plane belonged to a mission. ("The 23rd Psalm")
How was a plane which took off from Nigeria crash on an island which is supposedly in the Pacific?
How did DHARMA know about the Island, and how did they find it?
They used photos and information previously gathered by the U.S. Army who visited the Island in the 50's. The Island was found when a "clever fellow" constructed the Lamp Post station in which a pendulum revealed where the Island was most likely to be at a certain point. ("316")
Why were there no signs of DHARMA personnel on the Island in 2004?
What are the pregnancy issues experienced on the Island?
Women who got pregnant on the Island after 1977 could not carry their children to term. Sometime before the third trimester, the women experience a serious miscarriage which kills both mother and fetus. Women who conceive off-Island, such as Claire, give birth without issue. In addition, women such as Sun who conceive on island but leave before their third trimester, escape miscarriage and death. ("Do No Harm") ("Not In Portland") ("D.O.C.") ("Ji Yeon")
How does the Island affect the pregnant women?
The pregnancy problem is a consequence of the Island's electromagnetic energy, harming only those pregnant women and animals who receive direct exposure. Unfortunately, following the Incident, a previously sealed pocket of electromagnetic energy was released and continually "leaking", affecting all pregnant women on the Island, no matter their proximity to the electromagnetic source. ("LaFleur") ("The Incident, Parts 1 & 2") ("The New Man in Charge")
What does the Island do to the reproductive systems of its inhabitants?
Men experience a five-fold increase in sperm counts while on the Island, possibly due to the healing properties of the Island. ("Not in Portland") ("D.O.C.") Women's changed immune systems attack the fetus. ("One of Us)" ("The Other Woman")
What prevents women who conceived on the island from giving birth?
Their immune systems attack the new fetus as a pathogen. ("One of Us") ("The Other Woman") Women who conceived off-Island lack the immune boost when the zygote first implants.
They discovered the Wheel while digging to the Heart. Since Dr. Chang stated that they did initially plan to use the electromagnetic energy to time travel, they most likely studied the wheel and/or the time fluctuations related to it to determine how to harness electromagnetism for such purposes as time manipulation. ("Because You Left")
How was the wheel accessed and installed, as it predated the DHARMA station?
The Man in Black built the original wheel and came up with the plans to use it, though it was buried with his well before he could install it. He had many remaining years on the island to build another one or restore the original. ("Across the Sea") Hieroglyphics around the wheel suggest an Egyptian involvement. ("This Place Is Death")
Why was the wheel and the room it resided in frozen?
Ben eluded to the cause when he moved the island. Ben told John he was going somewhere cold and put on a Dharma Initiative parka. It is also plausible the DI knew this as well since they were testing the effects of the wheel on Polar Bears.
Claudia's people dug them out of scientific curiosity, noting that metal behaved strangely at certain sites on The Island. The Man in Black joined their effort so he could reach the Heart and use it to escape the Island. ("The Last Recruit") ("Across the Sea")
The Heart is the electromagnetic core of the island. The electromagnetism found deep within the island originates here and exists in its most powerful form. It radiates out to other parts of the island. ("The End")
Why must it be protected?
The Heart must be protected because if the energy is released, it could cause a global catastrophe. Similar to the Swan Incident, the electromagnetic expulsion caused the island to shake, but much more severely. Cliffs began to collapse into the ocean, and the shaking ground caused landslides and rockfalls. If it had escalated, the implications could have been disastrous. ("The End")
Why did a psychic tell Claire that she must be the one to raise Aaron?
Richard Malkin later revealed to Eko that his psychic abilities were a scam, thus his predictions for Claire weren't accurate. ("?")
Who was the couple in Los Angeles who could raise Aaron?
Although possibly a coincidence, since Malkin revealed that he was a fraud, Jack and Kate briefly lived together and raised Aaron in their time off the Island. Later still, Kate said she and Claire would raise Aaron. ("Something Nice Back Home") ("The End")
Why did Malkin change his prediction later, saying that Claire must give up Aaron to a couple in L.A.?
After Malkin's original prediction, his daughter drowned but awoke on the coroner's table. Rather than believing in the resurrection, Malkin interpreted his wife's belief in it as criticism of his own dishonesty. He spoke to a priest about the matter and contacted Claire shortly afterward, reversing his advice, having supposedly found a couple for her child. ("?")("Raised by Another")
How did Richard Malkin know Flight 815 would crash?
Richard Malkin later revealed that his powers were of a fraudulent nature, although his insistence on Claire taking specifically Flight 815 led her to believe he knew it would crash and force her to raise the child. It is unknown if any real psychic phenomena was at play in this scenario. ("Raised by Another")
Why was Claire never seen getting on the helicopter with Aaron as Desmond predicted?
As already stated, the outcome of a vision will always happen, though it can be delayed or the specifics can be changed. Claire didn't leave with Aaron on the helicopter, but each eventually flew off the island. ("The End")
Why did Desmond's flashes stop after Charlie died?
There was a wooden ankh inside, containing a list of the names of the survivors who came to the Temple (Reyes, Kwon, Jarrah, Shephard and Austen). ("LA X, Part 2")
Why did Hurley have a guitar case?
In addition to holding the ankh for delivery to the Temple, the guitar case may also have helped Ajira 316 to reach the Island by acting as a proxy for Charlie's guitar case on the original flight. ("Exodus, Part 2") ("316") ("LA X, Part 2")
Ben, under orders from Charles Widmore and assisted by a young Ethan Rom, went to Rousseau's tent in an attempt to kill her. However, he noticed her baby daughter, and in a quick change of heart he abducted Alex and spared Danielle, telling her to stay away from the Whispers in the jungle. Following this, Ben started taking care of Alex as his own child. ("Dead Is Dead")
He was instructed by Benjamin Linus to infiltrate the survivors in order to create lists of passengers who would be deemed acceptable recruits for the Others. After discovering that Claire was pregnant, he kidnapped her in order to help the Others research their fertility problems. ("Maternity Leave") ("A Tale of Two Cities") ("The Other Woman")
What was he doing when he was ensnared by Rousseau?
He informs John Locke that he was on his way to kidnap him, although, since aspects of his description of the Others have proven false on other occasions, this may not be true. ("Two for the Road")
Who was the real Henry Gale?
The real Henry Gale was a balloonist from Minnesota whose balloon crashed on The Island while he attempted a solo journey across the Pacific. He was killed by The Others and buried in an unmarked grave below his balloon. ("Lockdown") ("Dave")
It was designed by the DHARMA Initiative to conduct experiments on subliminal messaging, and to brainwash and interrogate abducted Hostiles. After the Purge, it was taken by the Others and it was used for experimentation and brainwashing as a mean of punishment. Widmore's team used it as a place to keep prisoners. ("The New Man in Charge") ("Not in Portland") ("Room 23") ("The Package")
A number of inscriptions inside are in Hieroglyphics, suggesting an origin dealing with ancient Egyptians. ("Lighthouse")
What is inside of the Temple?
Its primary function seems to be in surrounding the Temple Spring, just beyond the courtyard. However, it also houses the working quarters for Dogen, a high ranking Other and leader of the Temple, a machine to test for the presence of sickness in a person, and secret underground passages to different exit points around The Island. ("This Place is Death") ("LA X, Parts 1 & 2") ("What Kate Does") ("Lighthouse") ("Sundown")
What is the purpose of the Temple wall, and who built it?
The Temple wall was built by the Others to conceal and block access to the Temple by outsiders. ("Dead is Dead")
What is the purpose of the tunnels beneath the Temple?
The hieroglyphics in the chamber in which Ben had his run-in with the Monster seem to suggest that it is a chamber in which the Monster judges people. ("Dead is Dead")
Why were Daniel and Miles specifically selected for the mission?
Daniel was assigned to calculate bearings for the freighter's journey. Miles' ability to communicate with the dead was to be useful in locating Ben. Additionally, Daniel was Widmore's son who he apparently wanted the Island to heal. Besides these intended roles, Widmore and Eloise both recalled Daniel's 1977 actions and death. They knew that sending him to the Island in 2004 would cause the events that already occurred, including "the Incident". ("The Variable") ("Some Like It Hoth")
Tom found Michael as he was attempting suicide and persuaded him that he couldn't commit suicide as the Island wasn't done with him. He told him that the only way to redeem himself is to go as the Others' mole on Widmore's freighter and destroy it, to prevent the crew from arriving on the Island and killing everyone on it. ("Meet Kevin Johnson")
He was a theoretical astrophysicist, and high ranking member of the DHARMA Initiative responsible for many different aspects of the initiative, such as acting in orientation videos and overseeing various stations' construction. ("Because You Left") ("Some Like It Hoth")
Drilling into the massive pocket of energy beneath the Swan work site, ("The Incident") though it is possible that the survivors also caused some of the damage by detonating the Jughead, as "whatever happened, happened" still applies. ("The Incident") ("The End")
How was the Swan station preventing a similar Incident in the future?
In preparation for armed conflict against the hostiles. This was Radzinsky's original plan, although Kelvin may have continued it less with the interest of preparing for war and more just to provide a constant through his dull hatch life. ("Lost Encyclopedia")
Because the DHARMA facility in Guam, where the supplies were packed and sent from was still in operation until 2010. They didn't know that DHARMA ceased to exist after the Purge, receiving regular updates and coordinates from the Lamp Post station, whose mechanism for calculating the Island's position was programmed to run perpetually. ("The New Man in Charge")
There had been a long-standing feud between the Hostiles and DHARMA, each claiming some right to the Island. Although the two had struck an uneasy truce, the Initiative broke it multiple times. Eventually, Charles Widmore, the Hostiles' leader at the time, gave the order to exterminate the DHARMA initiative. ("The Man Behind the Curtain") ("LaFleur")
Were there any survivors from the DHARMA Initiative?
Electromagnetism existed on the island for thousands of years, concentrated in specific pockets. ("Across the Sea") In the late 1970s, the DHARMA Initiative drilled into one such pocket, releasing its energy. The survivors of Oceanic 815, who had traveled to the past, attempted to stop the incident by detonating a bomb. Their attempt failed and may even have contributed to the Incident. ("The Incident, Part 1")
What was the failsafe?
Turning the failsafe key could destroy the Swan. Doing so was considered dangerous and unpredictable, as the failsafe could only be activated from directly underneath the station. ("Live Together, Die Alone")
The Staff was a medical facility built by the DHARMA Initiative. It was later used by the Others as the place they would bring pregnant women to give birth and die, due to the problems experienced by pregnant women on the Island. ("D.O.C.")
Why was there a fake beard and clothes at the station?
They were used by the Others to fool the survivors of Oceanic 815 and possibly other unwanted visitors on the Island into thinking the Others were much less advanced people than they really were. ("Maternity Leave") ("Live Together, Die Alone")
Why did the station appear abandoned?
Because the Others had hidden all the medical equipment in a secret vault. ("D.O.C.")
The Pearl was a station designed to monitor the other DHARMA stations via hidden surveillance cameras. In the orientation video for the Pearl, "Mark Wickmund" claimed that the inhabitants of the Swan were unknowingly participating in a psychological experiment and that it was of vital importance to record every activity undertaken by the people in the Swan. ("?") ("The Cost of Living")
Why did the orientation video say that the events in the Swan were merely a psychological experiment?
Desmond had speculated that it was the inhabitants of the Pearl who were in fact undergoing a psychological experiment. It is also possible that the Pearl was a safeguard after the incident to ensure that the button was being pressed. ("Live Together, Die Alone") ("The Incident")
Why were the booklets from the Pearl simply left in the jungle, unretrieved?
Because although the Pearl operators believed the Swan personnel were the ones undergoing a psychological experiment, it was in fact themselves who were the experiment. DHARMA had no actual use for the journals or what was inside them. ("Live Together, Die Alone")
Why was the dirt over the Pearl salted to be visible from above?
Most likely for Pallet Drops by the planes that supplied the Island. ("?")
The Flame was used to communicate with the other DHARMA stations, as well as the outside world. ("Namaste") ("Enter 77") ("One of Us")
Why did Mikhail say its communications had been knocked out?
Because the discharge caused a massive electromagnetic anomaly which destroyed its communication capabilities, or so Mikhail claimed. However, it is likely Mikhail was lying about this in order to fool his Oceanic 815 visitors. ("Enter 77")
The Tempest was used to research and develop chemical weapons. It may have also been intended as a weapon against the hostiles, even though it was later ironically used by them against the Initiative. ("The Other Woman")
Why were the scientific labs hidden far underground beneath a greenhouse?
Because they were built in secret from the hostiles, whose truce with the DHARMA Initiative mandated that the Initiative could not drill more than ten feet into the ground or disturb any ancient ruins. ("The Truce")
The Lamp Post was used to locate the Island by predicting its most likely location at a given point in time. ("316") It also sent automated messages to the DHARMA logistics warehouse in Guam to send supply drops. ("The New Man in Charge")
How did Eloise Hawking come to be in charge of the Station?
Who was the "very smart man" who invented the algorithm to allow the DHARMA Initiative to find where the Island was going to be?
Why was Sayid in Ilana's custody on Ajira Flight 316?
Primarily she claimed that she was a bounty hunter hired by Peter Avellino's family to apprehend Sayid ("He's Our You"), though it was later revealed that she did this to bring Sayid to the Island, as part of her role as the person responsible for protecting Jacob, and later the remaining candidates. ("The Incident, Part 1") ("Ab Aeterno")
Why did Ilana get so emotional because of Jacob's death?
He was the closest thing to a father she ever had. ("Dr. Linus")
What was Ilana and Jacob's relationship?
He was a person she heavily trusted, ("Ab Aeterno") even as far as spending her whole life beside him training to one day protect his candidates. ("Everybody Loves Hugo")
How did Ilana leave the Russian hospital soon enough to capture Sayid, even though she was badly injured?
Crewmen from the Black Rock, according to supplementary DVD material. Damon Lindelof, however, later referred to the mystery as a forever "unchecked box", suggesting that that material is non-canon.
How was the Man in Black able to enter with the ash circle in place?
The ash circle was broken through unknown means some time before Locke and Ben initially went there.(The Lost Encyclopedia)
Why did Ben think Jacob lived in the cabin?
Jacob did at one time reside in the cabin. He later moved back to the statue, the ash circle was broken, and the Man in Black began using the cabin. Richard either forgot to mention to Ben that Jacob had moved or purposely misled him into believing that Jacob still used the cabin.
He was once a man, Jacob's twin brother and Claudia's second son, raised by Mother. He was keen on leaving the Island, though Mother constantly prevented him from doing so, eventually culminating in her killing Claudia's people, leading the Man in Black to kill her. Jacob, angered with this, threw the Man in Black into the Heart, making him the Monster. ("Across the Sea")
Jacob selected the candidates because they were "like him": alone and looking for something that was missing in their lives. ("What They Died For")
How was Jacob able to get the candidates to the Island?
At some point in each of their lives, Jacob came to the candidates off the Island and physically touched them. According to the Man in Black, somehow this touch caused fate to take control over the events in the candidates' lives, which eventually led them to the Island. ("The Incident") ("The Substitute")
Why was Kate not a candidate?
Jacob removed Kate's name when she became a mother to Aaron. According to Jacob, her removal as a candidate was only a line of chalk in a cave and she could take the position if she wished. ("Eggtown") ("What They Died For")
Which of the two Kwon's were actually one of Jacob's candidates?
Although Ilana seemed unsure whether Jin or Sun was the actual Kwon candidate, given that Jacob had removed Kate from his consideration when she became a mother, it is likely that Sun was not the candidate for the same reason. ("What They Died For")
Who was the final candidate?
Jack decided that he would accept Jacob's offer and became the new protector of the Island. His position was short-lived, however, as he was fatally wounded battling the Man in Black and died shortly after he prevented the Island from sinking. Hurley then took over the job, advised by Ben. ("What They Died For") ("The End")
She was the protector of the Island prior to Jacob. ("Across the Sea")
Why did the Man in Black refer to her as a "crazy" person?
She killed the Man in Black's birth mother and stole him and his brother from her. She also prevented him from leaving and massacred his people. ("Across the Sea")
What were the growing pains he had because of her?
She made a rule preventing him from killing Jacob, the man he held responsible for the loss of his humanity (by turning him into the smoke monster), and for his inability to leave the Island. She also prevented him from leaving the Island via the Wheel, and killed the people he was living with, preventing him from getting help from them. ("Across the Sea")
Why did she thank the Man in Black for killing her?
Their feud started when Ben disobeyed Widmore's orders to kill Rousseau, and later Alex, who he adopted and raised as an Other. ("Dead Is Dead")
Under which circumstances did Widmore leave the Island?
He was banished by Ben, who discovered he had a child with an outsider and frequently left the Island, which broke some of the Rules that the Others (or at least their leaders) followed. ("Dead Is Dead")
Because after Ishmael Bakir, an associate of Widmore's killed Nadia, Ben manipulates Sayid into thinking he can revenge his late wife and protect his friends by joining Ben. ("The Shape of Things to Come")
Who were the people that Sayid was killing for Ben?
No. Events in the past already occurred. Their consequences, which future people witness, prove what occurred. Regardless of past peoples' motivations and their knowledge of the present, they eventually chose a specific course of action, one that produced the present's current state. ("Because You Left") ("The Lie")
Can major events change the timeline?
No. Daniel Faraday briefly hypothesized that a sufficiently major event, such as detonating a hydrogen bomb, could undo past events. He was later proven incorrect. Although it initially seemed that such actions caused the timeline to diverge into parallel branches, the events in the flash sideways took place in the afterlife, long after the crash of Oceanic 815. ("The Variable") ("LA X, Part 1") ("The End")
Why was the Island submerged in the flash sideways timeline?
Due to the revelation that the flash sideways world was actually the afterlife, it is likely that the Island being submerged was a narrative device to indicate that the Island held no power over the lives of the Oceanic passengers. ("LA X, Part 1") ("The End")
What happened to Locke's knives and Christian's coffin?
Within the context of the flash sideways, Oceanic Airlines simply misplaced the items. ("The Substitute") ("The End") The characters created the world of the flash sideways and sought to let go of obsessions and remember significant experiences. Losing and recovering their literal baggage helped them along this path. ("The End")
How was Jack's life different in the flash sideways timeline?
In the flash sideways timeline, Jack had had a son with Juliet Carlson. Though he strove to be a better father than Christian, Jack's relation with his son David was strained. Despite this, Jack was able to patch up his relationship with David; something he had never been able to do with his own father. ("Lighthouse") ("The End")
What caused Jack's recurring neck wound?
The neck wound was an artifact from Jack's life on the Island, where the Man in Black attempted to stab him in the neck. ("The End")
Why did the wound keep reappearing?
Given that the flash sideways timeline had been created to help the Oceanic survivors remember their former lives, the neck wound was likely meant to help Jack remember. ("The End")
What did he want to show to the rest of the Oceanic 815 passengers?
He wanted to show them that this wasn't their real life, that it was actually their afterlife, and wanted to help them all remember their past lives, and fulfill their purpose in the flash sideways timeline (Hurley finally going out with Libby, Locke "letting go", Sayid meeting Shannon, Claire meeting Charlie, and Jack and Kate coming together). ("Everybody Loves Hugo") ("The Last Recruit") ("What They Died For") ("The End")
Why did he run Locke over?
He wanted him to meet Jack again (this time as his patient), so he can have the surgery and finally "let go". ("What They Died For") ("The End")
Christian Shephard explained to Jack that everyone in the church was real. Juliet and Jack did not have a son together in their Earthly lives, so David was apparently a surrogate, needed by Jack to help him overcome his father issues, and by Juliet, herself a fertility specialist, to reconcile never having a child of her own. ("The End")
When Juliet was near death, she was able to see a vision of the afterlife, wherein Oceanic 815 never crashed. She may have incorrectly assumed that they had been successful in preventing the Incident, resulting in Oceanic 815's safe landing in Los Angeles. However, she also said to Sawyer as she was dying, "We should get coffee sometime. We can go Dutch." Later, when she met him at the vending machine in the flash sideways, she said the exact same thing about going Dutch for coffee, followed by "It worked," referring to the trick she suggested for getting Sawyer's stuck candy bar out of the machine. So it is possible that those last thoughts, "It worked," that Miles detected from her grave, were actually her seeing her afterlife, and repeating what she said to Sawyer at the machine. ("LA X, Part 1") ("The End")
How was Charlotte Malkin able to communicate with Yemi?
Similar to Juliet, when she was close to death via drowning Charlotte Malkin was able to see into the afterlife where she presumably spoke with Yemi who gave her a message for Eko. ("?") ("The End")
How is Desmond able to see visions of the flashsideways timeline?
Since exposure to large amounts of electromagnetism can cause characters to see visions of their past and future, Widmore's experiment forced Desmond to see so far into his own future that he was looking at his own afterlife. ("Happily Ever After") ("The End")
How are the flashsideways characters able to see the events from the original timeline?
Since the timelines were not actually separate, and the flashsideways timeline was the characters' afterlife, these visions occurred when characters were able to make some sort of connection with their previous lives, granting them awareness of the events they had previously lived out. ("Happily Ever After") ("Everybody Loves Hugo") ("The End")
Michael wasn't at the church because he was trapped on the Island as a ghost for having murdered Ana Lucia and Libby. Walt likely wasn't there because the Island (and thus the Oceanic castaways) were no longer a part of his life. The most important part of their lives were the time they spent together. This indicates that Walt and anyone else capable of moving on, likely has a different experience and set of people, unspecified, to move on with, and did not contribute to the creation of the Island survivors flash sideways world; he had "been through enough." ("Two for the Road") ("The Life and Death of Jeremy Bentham") ("Everybody Loves Hugo")("The End")