The pain of 9/11 remains unresolved because the crime of 9/11 remains unsolved. In 17 years no one has been prosecuted for carrying out the attacks, and the court of public opinion is very much a hung jury.
The Range of Views about 9/11
The same range of interpretations that sprung up in the wake of the attacks are still being recycled and restated on this anniversary.
A) The attacks were planned and carried out entirely by Al Qaeda operatives, led by Osama Bin Laden. No one in the US bears any responsibility and therefore the war on terror is entirely justified.
B) The attacks were blowback from Western support for the mujahideen in Afghanistan (and, much less often acknowledged, in the former Yugoslavia and elsewhere). The war on terror may have been an overreaction, but it is still fundamentally necessary.
C) The attacks were perpetrated by Al Qaeda but were allowed to happen by people within the Bush administration and the US government more generally. They used 9/11 as an excuse to launch the war on terror, which is mostly a sham.
D) The attacks were perpetrated by elements within the US government (some say the White House, more intelligent people say within the CIA, NSA and DOD) either with the help of Al Qaeda or otherwise. The war on terror is a total sham.
Any serious assessment of the merits and demerits of these different views, especially the latter two with regard to possible foreign state-sponsorship, would take too long for anyone to read. One of the best investigations is contained in Jon Gold’s We Were Lied To About 9/11, a highly accessible and informative (and free) e-book. Rather than rehash Jon’s book I’ll simply implore you to download and read it for yourself, and I’ll confine myself to what I think are the most important questions about the 9/11 attacks.