A common logical fallacy amongst the 9/11 truth movement is called special pleading. To explain this concept I summon Carl Sagan and his definition of special pleading found in his book The Demon-Haunted World:
special pleading, often to rescue a proposition in deep rhetorical trouble (e.g., How can a merciful God condemn future generations to torment because, against orders, one woman induced one man to eat an apple? Special plead: you don’t understand the subtle Doctrine of Free Will. Or: How can there be an equally godlike Father, Son, and Holy Ghost in the same Person? Special plead: You don’t understand the Divine Mystery of the Trinity. Or: How could God permit the followers of Judaism, Christianity, and Islam – each in their own way enjoined to heroic measures of loving kindness and compassion – to have perpetrated so much cruelty for so long? Special plead: You don’t understand Free Will again. And anyway, God moves in mysterious ways.)
So how can this notion be applied to the 9/11 truth movement? The following is a common example of special pleading (e.g., How can the govt. continue to conceal the conspiracy if literally thousands of people were involved? Special plead: you don’t understand the concept of compartmentalization within the government).
This argument is special pleading because it avoids having to answer the real problem, namely that even with compartmentalization there still remain thousands of people who have to remain silent. Lets take the people who set up the demolition charges for instance. If they were only given instructions to set charges and nothing else, then I find it a little odd that not a single one of them has come forward with this information. The notion of compartmentalization fails when we realize that if one link in the chain fails, then the entire conspiracy fails.
Compartmentalization is a very real thing, but the problem with applying it to 9/11 is the scope of it is too large. As the example in the preceding paragraph proved, the people involved with the set up of charges in the twin towers now realize precisely why they were not told any more information. Those same people who wired the buildings for destruction have watched the videos of the collapses and (barring an inconceivable amount of idiocy) now realize the larger scope of the plan.