There is no uniform answer to what truthers believe, but the general idea is that the 9/11 attacks involved a conspiracy of some sort, which allowed people within the government to perpetrate a hoax, a sham attack, the equivalent of the Riechstag fire, with the goal of advancing some agenda, involving removing civil liberties, advancing the interest of certain private parties, and expansionistic military adventures by the US.
The main positive evidence in the case of 9/11 is the collapse of WTC7, which is inexplicable. A building which wasn't hit by airplanes was demolished that day, in a collapse that resembled the WTC collapse, and this causes cognitive dissonance. But it is difficult to draw definitive conclusions from a single anomaly.
Chomsky's Complaint
There is a serious,superficially insurmountable, obstacle to any such conspiracy idea, explained also in other answers, which must be adressed first in order to become a truther.
In order to proceed with this line, one must first answer Chomsky's question: How the HECK can you have a nefarious conspiracy of 3,000 officials and not have word leak out? It is simpy impossible to imagine such a thing, because you can't even trust a dozen people with a secret, somebody always opens their big mouth. To trust the thousands and thousands of people involved in faking such an attack is completely ludicrous, it is beyond preposterous, it is impossible.
But the recent Boston bombing attacks have provided an answer to this. The main point is that there was a drill simulating the events, simultaneous with the events themselves.
When you have a secret drill, coinciding with actual attacks, it is possible to do all the arrangements for the attack as part of the drill, without the people involved in the drill even suspecting that they are somehow coordinating the attack. In fact, afterwards, the people involved in the drill will feel like they are prophetic--- their predictions for the attack were SPOT ON! They did an excellent job in thinking like a terrorist! They deserve promotions, they predicted the attack to a tee.
A Fictional Scenario
A top official arranges a drill involving at least two tiers of secrecy. The lower level of the drill involves people with a low security clearence, the higher level of the drill involves people with high security clearence, and the nefarious plot is only known to the top official and a handful of other co-conspirators, who are not communicating through government channels at all.
The drill is designed to "think like a terrorist" and figure out how to plant bombs, or hijack planes, or do some destruction. People with low security clearence sit around and think about how terrorists might do it. People get reports about it, they send them up, and they are each classified on the higher security level, so that only top level folks can see all of these.
Then the conspirator picks out one of the plans produced, and puts them into operation. Sending the plan down to the bureaucracy again, he asks people to build a simulation of this plan. For example, to produce a drone the size of a commercial airplane to hit a building, as part of a simulation. The work is done by people at a lower level of security clearence, and the thing is classified with a high security clearence. All that the conspirator has to do is manipulate security clearences.
Nobody who is doing this remotely suspects that the drone they are working on is going to be used to do actual terrorism. Once the drones are built, they are painted to look "realistic" for the simulation, and the people involved are doing a terrorism drill, they don't suspect anything. As part of the drill, you have military planes shoot down the drill drones, to practice taking out commercial airliners.
Except, unknown to them, they aren't shooting down the drill drones, you send the pilots the coordinates of actual commercial airliners, and they shoot these down, killing everyone on board (they don't know this, and they do this hours before any attacks). Then you fly your two drones (you have made two using a duplication of effort, each hidden from the other) into the twin towers.
In the previous period, you have 1-2 people, private CIA explosives contractors, with coordination with the building owner (and nobody else) put explosives in the building, at each story, to knock it down once the drones hit the building. You promise the owner compensation in exchange for secrecy, and you say the following:
Official: As part of terrorism awareness, knowing that your building has been a target of terrorism in the past, in case of a terrorist attack, we might have to demolish the buildings to ensure the safety of other buildings in the area from the collapse of certain part of your building. This means we should rig your building for demolition in case of attack.
Owner: But who the heck would rent in a building which is rigged to collapse?
Official: You can be assured that the buildings will be rigged in secrecy, only you will know about it, your tenets will be clueless. Please provide us with structural plans so we can do the rigging, to ensure safety in case of collapse.
Owner: Ok, but I am afraid word will get out.
Official: Don't worry about this, we will use a special secret squad consisting of 2 highly trained and highly reliable operatives, and they will do this in the middle of the night, into the early morning, every night, over several months. By the way, we also have suspicious intelligence that suggests an attack of this sort might be brewing, and it is best for you to be careful.
The owner then gets a shitload of insurance, because he is scared as heck of a potential terrorist attack. He cooperates with this, but keeps his mouth shut, because he doesn't think anyone would rent from him thinking his buildings are rigged to go down. They sit there, rigged to go down for months.
Then the planes hit, and the controlled collapse is authorized by the official, and the 2 operatives bring the buildings down. The owner now DEFINITELY doesn't want to admit he allowed this, because he is now partly responsible for 3,000 deaths, and he feels both guilty and scared of being sued and imprisoned for allowing this. But he doesn't think "I am part of a conspiracy", because it is all done in secret, and he doesn't know about the other parts of the conspiracy.
But he doesn't want anyone to die, and he tells people to get the hell out of the buildings before they come down, and then he kicks himself for using demolition language. The CIA folks doing the demolition think they are ensuring public safety, and have no reason to come forward. They only know one little part of the conspiracy.
The number of people involved in the actual conspiracy, the people who know that the attack is fabricated from start to finish, could then be reduced to as small as four people--- one very high level official, who can control classification status and has decades of familiarity with the bureaucracy, and a few other people who know how to pilot drones. All the other people, the CIA explosive expert who plant the charges in the buildings, the building owner, only know a little bit, and think they are acting in the interest of public safety, or terrorism prevention. The people shooting down the airliners, or the ones building the commercial airliner drones, part of a terrorism drill. The people who arrange the drones, the people who shoot down the jetliners, the people who do whatever else, all are doing everything as part of the "scheduled drill". The people who demolish the building think they are doing so for the safety of the public, as the buildings are going to collapse anyway, due to the jeliner impact, causing more destruction
Further, you get together 16 passports of Saudi people who are missing or killed by the CIA, without relatives, and you create paperwork about these terrorists, simply by bringing down documents from a higher to a lower level of secrecy. You also put your drill report as part of the government paperwork, all this is done as part of terrorism awareness, and in each case you ask low-level people to supply information on a possible suspect, and you take whatever bullshit they give you back, and you make it part of the top-secret records.
Then once the attack happens, you release information little by little, and manage the information. When the terrorists are needed, you supply passports and stories about these people. It really is not an enormous conspiracy, it's a tiny conspiracy.
What the story requires
But it absolutely requires ONE THING, a terrorism drill! You can't do it without having a drill around the whole event, which miraculously matches the event. This is the sine-qua-non, it can't be done any other way. You need to have people making plans for the event, building bombs, making drones, whatever, and they must be doing it for a terrorism drill which matches the event in complete miraculous, almost spooky, fidelity.
It is a notable fact that each of the following events have precisely coincided, in uncanny ways, with a drill to simulate their consequences:
Each of these coincided with a drill, which spookily matched the exact nature of the events. The 9/11 attack coincided with a plan to simulate flying a plane into a building, as part of a terrorism prevention plot. The 2005 London bombing coincided with a drill that simulated bombs in 4 stations, the exact 4 stations where the bombs actually hit, on the same day. The Sandy-Hook shooting matched a plan to simulate a terrorist attack on children, and the Boston Marathon bombing coincided with drills to simulate an explosion in the Boston marathon.
So it is precisely in these cases that we see that it is possible to produce the sham attack without a large conspiracy, and the attack matches the drill. That does not mean it happened according to the fiction story, but it does not require an enormous suspension of disbelief in the laws of human organization to see that it can happen.
How to prevent such things
Simple! No more secret terrorism drills. One is better of being unprepared for terrorism attacks, which happen rarely, and in and of themselves are extremely non-threatening to the social order, than to allow the potential for coordinating a real attack from within the government, under the cover of a drill. You can live with a few terrorist attacks, you can't live with a government that takes over your life.
Further, without the government instigating them, the number of terrorist attacks in the US would probably be close to the 1900-1990 average, which is approximately zero attacks per year. The US isn't Israel, it is not a very attractive terrorism target, nobody sane wants to attack it.
In order to reassure the suspicious public, the secret societies in the government, the tiers of secret documents, must be completely opened up.
How to disprove these scenarios
You simply have to review the drill documents in detail, and interview every single person involved, to make sure that there was no way the drill could have been manipulated to turn live. At the moment, I can see a path for it to happen, and since the anomalies, which are especially serious in the case of the Boston bombing, are impossible to make sense of except for a drill which turns live, and the information is manipulated from inside the government, I am a truther.
I am also happy, and have no intention of comitting suicide, now or ever, I have a lot to live for. But I AM thinking about finding another country in which to live, because the current situation in the US is absolutely intolerable.
What can the public do?
Simple! Ignore terrorist attacks, and focus on civil liberties. Elect people who promise to preserve civil liberties in the face of "terror", and open up secret documents as quickly as possible, to prevent such plots from even being possible in the first place.
The most nefarious deeds of governments are conducted under the cover of secrecy. The genocides of the 20th century, the bombing of Cambodia, the CIA coups, the torture and rendition. It is important to remove the potential for misdeeds. There is no need for a CIA anymore. The cold war is over.
Unfortunately, the public already tried this with Obama, and Obama has failed to open up the secrecy layers, instead inhabiting and promting the secret society he promised to kill. Perhaps Jesse Ventura would be a better president in this regard.
At the moment, I feel that all social and economic policy should be secondary to this consideration, removing the power of individuals within the government to stage terror through secrecy and drills.
See here: Another official drill goes live after Texas fertilizer plant explosion
Your scenario for 9/11 is the most believable explanation of what happened that I've ever heard, by a mile. Are you able to create similarly-plausible scenarios for, say, sandy hook or Boston? These events also had corresponding drills, but how exactly they might have been pulled off by a "conspirator" is somewhat mysterious to me.
(The more I read about Sandy Hook in particular, the more puzzled I am. For example, drill footage was unquestionably used in media reports on Sandy Hook, footage from the same day at the other school, and also it seems from the October drills at SH itself. But it still seems like there would be too many mouths to shut.)
These recent attacks are completely nuts, they are so absurd and so obviously fabricated, but there's no motive! I didn't even read about them, since I don't follow the news, except after getting the conspiracy idea for 9/11. I don't know what to make of them. I had one crazy fleeting thought that this is John Kerry's way of alerting people to what happened on 9/11, by pulling off completely incompetent stunts that people should be able to see through immediately, but this is absurd spy-vs-spy fantasy. I just don't know.
The 9/11 story I told is probably wrong in the details, but I think it's close to the big picture. I found that people proposed something like this several times (like, flight of the bumble-planes). The main issue with the precise scenario is hiding the plane crashes (flight 77 has a reported crash on the KY border). But there is a way to get this done (cribbed from bumble-planes)--- you can pretend the planes are hijacked and transfer the passengers to flight 93, and then this airplane can be shot down. This can be done at an airforce under orders, as part of the drill, and nobody needs to know the flight number.
The idea of doing everything via drill is extremely important, because it reduces the conspiracy to order 1 person, which is the maximum allowed size.
I don't believe anything, but I can tell you why I am skeptical of the official version of 9/11 for reasons that may be different from others. I've been very skeptical since that day, but to understand my skepticism you must know what I knew at the time, which is:
From these I had already concluded that the U.S. government knew the towers were unsafe. I thought about what it would mean if either tower toppled over like a falling tree, which would destroy a large part of Manhattan. It would be horrific.
I am not a structural engineer. I have a technical background in many things, especially math, chemistry, and computer science, so I am able to read engineering and scientific papers in nearly every discipline.
So 9/11 comes along and I'm watching the whole thing on TV. My first reaction was, we are under attack; I even told my wife this. After a while, I remember a news anchor saying that one of the towers has a visible lean to it and I thought this is it; this will destroy a huge area of Manhattan, 10s of thousands at least will die and our economy will be ruined.
Then I watched the first tower fall down in a peculiar way that was most unexpected to me. It was a progressive failure like the building had been made out of cards. I immediately thought that the government had been prepared, thank goodness, and was able to control the tower's fall, no doubt with demolition, and I thought, wow there is no way they will be able to admit this.
I didn't know about building 7 until later. I saw the video of the collapse and became immediately suspicious. According to NIST, Building 7 collapsed in a progressive way similar to the two towers. OK 3 for 3 now, 3 buildings catch fire and collapsed in a progressive way and according to NIST it had never happened before.
So I am skeptical. The report on Building 1 and 2 collapse is large and I don't have the time to take it on. The Building 7 report is pretty short. So far I've been through it twice and there are a few things that stick out so far:
The NIST report says that no steel was heated to more than 600 degrees, most not more than 300 degrees. According to NIST Diesel fuel was not a factor and did not burn. According to NIST no other buildings of this kind have failed this way even though one burned for 18 hours and did not collapse. According to NIST the Collapse was started by the failure of a single column and progressed through the building so fast that the entire roof, as a single unit fell near free-fall to the ground.
You would think that a widespread building design that has tall buildings relying on a single "Hail Mary" column holding them up would have a lot of people up in arms trying to fix them all; especially in earthquake prone zones.
This idea is pretty much exactly what I believed from 2002-2011, the the government had a demolition system in the buildings since 1993, and misused it on 9-11 to prevent the buildings toppling over, but the attack was otherwise as the government said.
But this is simply not possible, because there is another coincidence that day--- the government had military drills simulatiing a multiple hijacking, at the same time as the "actual" hijacking. Without these drills (and other drills), the attack envisioned by the government scenario just wouldn't work, the planes would have been intercepted, and never would have reached their targets.
Unlike the demolition of the WTC, you can't cook up an innocent explanation for the drills. This is Webster Tarpley's point. So please, don't sit in this half-way house, it was not that there was just a demolition system. This attack was fabricated from start to finish, using drills.
The innocence or guilt of the government will come out if only we can get something investigated. A smoking gun, which to me is building 7.
You haven't seen enough political battles--- you never prevail just because you are right, otherwise history would be easy. You prevail when you have surpassed the other side by an enormous enough margin that they can no longer deny it, and join you.
Building 7 is a smoking gun for demolition (as are the WTC collapses, too, frankly). But you also need a smoking gun for the inside job, and these are the drills. It is important to not compromise, or meet other people halfway here, they are just totally wrong, and the truthers are totally right.
Do you have a link so I can do some reading
I suppose the world's expert on the drills is Webster Tarpley. He has compiled a list of related drills stretching back for a decade. But the work is expansive, and the relevant drills on that day are documented in several other places, you just need to dig a little.
The names of the drills disguise what they were doing--- they were simulating multiple simultaneous hijacking, including crashing into buildings, in several unrelated exercizes that happened to coincide with 9/11. The names are "Vigilant Guardian" "Vigilant Warrier" "Northern Vigilance" "Northern Guardian", the confusing identical names are a problem here.
Northern Vigilance sent fighters to the North, to deal with an imaginary Soviet (!) attack. I forget what Northern Guardian was about. Vigilant Warrior/Vigilant guardian was some sort of combination of exercizes to simulate response to simultaneous hijacking of planes. There are secret details here that didn't come out.
What is known for sure is that these drills mucked up the response to 9/11, because there were fake blips on the radar, live-fly drones in the air, and a whole bunch of distractions, and all the fighters were either up north or out to sea, so that there were only a handful left.
There were half a dozen more drills that day. There is no explicable reason for all these secret drills coinciding with the attack other than that the drills were used to stage the attack. If you use drills, you can in principle do the whole attack with no co-conspirators. One way to do this is explained in my answer here. The details are a little wrong--- the passengers are not killed on the planes, they were probably all transferred to the flight identified as flight 93, which was then shot down later. That makes more sense, since this airplane is widely known to have been shot down in truther circles, and the total number of passengers on the four planes would all together fit on one big plane (one of the inexplicable anomalies of 9/11). The excuse for the transfer is probably a hijacking exercize, there are reports that this was part of the drill package too, and this would resolve the phone-call issue, and there are no more anomalies.
The full story is not summarized anywhere, because there is no truther "standard model", but most of the MIHOP people agree on the idea of drills used to stage the attack, and all of them, MIHOP and LIHOP, agree on the demolitions.
The recent freedom of information release of ACARS and radar data show that the WTC flight flight 175 was swapped with one of the drill live-fly drone blips, and according to the ACARS went on to land in Cincinatti. Flight 93 also landed at Cincinnatti according to the ACARS data (this is mentioned in Loose Change, the primary data can be found on Pilots for 9/11 truth). The switches probably ended up placing everybody on the plane identified as flight 11, this was listed as destroyed afterwards. Flight 77 was also listed as destroyed, I don't know how that happened, that's the Pentagon plane. Perhaps this was shot down too.
You need to sort out the details here, there is no alternative. By the time the mainstream catches up, the people on the outside will already know everything. You can't rely on officials.
Good I will read about it, thanks