[Megan]  A reader asks the following question:

I had a thought; if anyone can get a gun, and shoot people, even teenagers, and obviously psychotic people, then why haven't any Islamist terrorists done so?
I mean, wouldn't they?  If a jihadist can go into Walmart, buy a gun and ammo, go back to his car, load the gun, and go back into the Walmart and shoot everyone in sight, then why haven't any of them done this?
Why?  why? why? I wonder!
I am starting to wonder, that maybe there aren't any out there. Could that be?  I have been so programmed to be en-guarde against the threat of Islamic jihadists, that it is hard to believe that they are not out there, plotting against us.  But then, why haven't they gotten guns to shoot us?  It would be so easy.
Could the threat be exagerated?  This question is not intended to be rhetorical; I would really like to know.

There are several possibilities:

  1. Our excessive homeland security is actually doing a good job of screening out terrorists
  2. The terrorists that are here can't buy guns legally, because they are illegal aliens
  3. The terrorists don't want to shoot people.

I assume that all three are true, but I'd bet that number three has the largest effect.  There are lots of spectacular things that terrorists could do to severely hurt the American economy, or kill lots of people in accidents.  No, I won't name any, but I can think of half-a-dozen off the top of my head, and I'm sure you could too.

But terrorists don't want to kill people in, say, spectacular car wrecks.  They want to kill people in ways that are spectacular, fear-inducing, and hard to defend against.  Spectacular, so they can raise money and recruits; fear inducing, so as to produce the desired policy response; hard to defend against, because if they are a one-time fluke, they won't induce fear.

Attacks like today's aren't actually that hard to defend against, not if they are common.  Arm the teachers; arm the students; put armed security guards in every building.  We don't defend against them because they are rare, not because we couldn't.

Bombs, on the other hand, are very hard to defend against, which is why Israel has had such a difficult time doing so.  It's worth noting that in fact many mass-shootings have been stopped by armed citizens, including one in Virginia recently.  Thus, while the attack might be easy to stage, it might have too low a probability of success to waste valuable human resources on.

Update: Another reader accuses me of missing the central question.  Let me clarify: I think that the threat from terrorism in America may be exaggerated (as almost any telegenic threat, like that of school shootings or forest fires, tends to be).  But this isn't good evidence of that.  Terrorists seem to favour bombs over guns worldwide; the question is why we aren't having more bombings, when a terrorist could surely slowly acquire the requisite amount of fertiliser as easy as this kid slowly acquired guns.