Quote Originally Posted by JKDS View Post
What of the person who kills for sport, and enjoys the challenge of it all? You're trying to say "ppl with guns deters other ppl with guns", but that only works with ordinary people...if it works at all. People willing to massacre Innocents are not ordinary. Their motives are different from ours.
Using the usage "massacre", how do they massacre those who can defend themselves? I ask this because I think the frame you are using assumes a type of preference that can be deterred. If a person is looking to massacre and there is sufficient reason for him to believe he won't be successful at massacre, he is deterred. However, if you are positing that somebody wishes to kill regardless of probability of success of outcome, then yeah they can't really be incentivized against it*. Though the casualties can be kept minimal through other means.

If a kid really wanted to shoot up his school, he's gonna try. Metal detectors be damned
The metal detectors deter the kid who wants to shoot up his school marginally.** Though it doesn't deter the kid who has sufficient desire and capability to bypass the metal detectors.

*In economics, this would be somebody sufficiently crazy that they don't know their own preferences or that their preference is to have low success at killing.

**This means that a kid who desires and is capable just enough to shoot up a school when there is no metal detector, yet is deterred when there is. Not all killers fall under this type of category, but some do. Also, everybody falls under a "marginal" category; there are just differences in what is marginally beneficial to each person.