Thoughts Arguments and Rants


As of July 8 I will be posting on Crooked Timber. This blog will keep running, but it will be more focussed on metaphysics, epistemology and philosophy of language than it used to be, with other posts going to Crooked Timber.


So I’ve decided to move to Blogger permanently. And to celebrate, let’s post on something of broader interest: gun laws. When there’s a shooting in Australia, the normal reaction is that we have to have tougher gun laws to stop them. In America (and, sadly, sometimes in Australia), the reaction is sometimes that there needs to be weaker gun laws so more civilians can stop them. The reasoning here is fairly simple. If everyone has a gun, and everyone knows everyone has a gun, and everyone knows that everyone is ready, willing and able to use their gun on the smallest provocation, and no one wants to be shot, no one will shoot anyone because they know they will be shot. There looks like there are a few possible problems with this theory, but who knows, maybe it works.

Of course, there is one rather dramatic problem with this theory. The US has the most liberal gun laws in the western world and has the highest homicide rates in the western world. How, oh how, then are we meant to believe that more guns leads to less crime? The answer is that we’re apparently comparing apples and oranges. The things we’re allowed to compare are regions that are adjacent in space or time. And if we compare region r at t with region r at an immediate subsequent time just after gun laws are tightened, the crime rate rises. (Or maybe it doesn’t rise, but then they say it would have fallen anyway, and would have fallen more without tight gun laws. Spot them that.) Or if we compare region r with tight gun laws with adjacent region s with looser gun laws, region s has less crime. In America, the regions are counties or states, which can change gun laws between areas. And that’s meant to be the conclusive evidence.

But it seems to me that this is less than conclusive, especially given the rather large elephant in the room that is the horrifically large American murder rate. It seems to me that there are three possible effects of tightening gun laws.

(a)      Decreasing the deterrence effect of having lots and lots of gun around, hence increasing crime.

(b)      Decreasing the access to guns of those wanting to commit crimes, hence decreasing crime.

(c)      Decreasing the cultural penetration of guns, and hence decreasing gun-related crime, and probably crime overall.

Which of these effects is the strongest? Well, that’s an empirical question, and we shouldn’t try and answer it from the armchair. But we can tell some things from what we know about those three effects. First, if (c) is an effect at all, it will be very delayed and very diffuse. So you wouldn’t expect to see it in the side-by-side analysis that gun-nuts run with, and would expect to see it in the country by country analysis that we gun-banners run with. That doesn’t prove anything, because if there’s no cultural penetration effect you wouldn’t expect to see it either.

The more interesting thing is that if (b) is an effect at all, and frankly it beggars belief to think that it isn’t, you also would expect it would be much weaker in side-by-side regions as compared to regions from quite different areas. The fact that guns can be carried across county borders and state borders with no hassle at all will mean that the access of guns in a region is a function of the gun laws in that region and adjoining regions. And plausibly something similar happens immediately after a tightening of gun laws, because non-criminals move into compliance with the laws before criminals do. So while there will be an immediate and local drop in the deterrence effect, there will be a slow and diffuse drop in the access and cultural penetration effects.

What does that imply? If (b) and (c) are large effects, then we’d expect that the side-by-side region data would not show this up, but would show that there’s a short sharp cost to tightening gun laws, because the only spatially and temporally local effect is the deterrence effect. In effect, various regions (or, more precisely, time-slices of regions) are playing a prisoners dilemma. Each has a motivation to slacken, or at least not tighten, gun laws. But the community of regions is best off if everyone tightens gun laws. Of course, trying to convince libertarians that a particular situation is a prisoners’ dilemma is a little harder than trying to convince an Australian of something so silly as that more guns leads to less gun crime, so I don’t expect this argument will get very far, but one can only try.

posted by Brian Weatherson 10/31/2002 11:01:00 PM


I'm thinking of moving my Brown hosted blog, now at, to here. For now keep going to that page, but this may become the standard.

posted by Brian Weatherson 10/30/2002 03:58:00 PM

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My random philosophical musings, more often in premise-conclusion form than is normal for this media


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