[dragonwriter]

> A healthy and minimally secure citizenry can be a public good just as much as roads and armies, which are also paid by taxes.

As a very narrow and specific (and not necessarily the most important) example of this, in any nation which may rely on conscription and/or mobilization of volunteer citizen militias in time of need, a healthy and minimally secure citizenry is, among other public goods, directly related to military capacity.