Quote from dpt:
The other problem is that the collapse clearly began in both towers very close
to the level where the airplanes actually struck, and it really strains
credulity to say that these levels could have been precisely known in advance
of the crashes.
Remember, in the minds of the conspiracy theorists, the fiendishly clever
government conspirators wanted it to be possible for the sheeple to think that
the airplanes were actually what brought the towers down, so it had to look as
if that could have been the case at least 
So it simply would not have been sufficient to prepare 2 or 3 floors for
demolition, you really would have to prepare 20 or 30, and then tell the pilots
to aim for roughly the right levels. But then of course, the whole buildings
might just as well have been more or less filled with explosives. So its
better just to insist that they could never have come down the way they
did unless they were wired from top to bottom, and had lots of big bombs
inside, to boot
BINGO.
I agree, and the CT'ers have provided no proof to refute the idea that if one floor of the structure at the impact level collapsed onto the floor below it, the force would easily be enough to cause the collapse of that severely weakened lower floor... and then things follow on from there. I admit I am not a structural engineer (unlike the CT'ers whose whole argument is based on an assumption that they can make very sophisticated analyses of structural dynamics).
But the real point is above. In any film footage of the collapse, what you see is the top section begin to fall. That is it. You do not see a series of times explosions evident on the outside of the building at all. We know that the structural support of this building was of the 'perimeter tube' variety. If demolition crews were to bring this building down
without the help of an airliner, they would have to plant charges at the site of the structural supports of the building - that is, at the perimeter tubes. However, we see absolutely no sign
whatsoever of times charges at these sites when the building collapses. Batgirl's 'squid' video is the exception that proves the rule. One little puff of smoke. So... the theory that the collapse was caused solely by preset explosive charges and that the airliners were a red herring is absurd on the face of it. We simply do not see the detonations at the perimeter of the building that would be necessary,
However, the CT theory could work if one believed that demolition crews had planted extensive charges at a few floors, with the idea that by causing a floor or two to buckle, the whole structure could be brought down (as actually happened). In this case... what is the theory? The demolition guys rigged up explosives at a few selected floors within a range and then the hijacker pilot was told to fly the plane into those floors, thus obscuring the sight of the actual detonations? Laura and Jeb Bush were airborne in a black helicopter and pressed the button at the instant that the planes impacted the building? If this is the theory, we can rule out the idea that the hijackers were piloting the planes at the moment of impact, or that they were not trained pilots. No plan which involves a precise flying job like this could depend on the skills of a pilot who had a few weeks in a simulator. Could even a skilled pilot fly the aircraft into a 40 foot vertical window at 500 mph on a wildly curving flight path, in the state of rapture that presumably goes with imminent martyrdom?
Way, way too complicated. Way too many questions. Wield Occam's razor and stop the madness.
