 Finally, at least for our purposes, game theory has been crucial to the analysis of many important problems in environmental ethics, the most famous probably being the tragedy of the commons (G. Hardin 1968) where game theory has been used to show how resources can easily be depleted or degraded when they are held in common and use of the resource is not regulated. The idea of the tragedy of the commons is that when access to a scarce resource is not limited in some way there is a tendency for use of the resource to exceed the environment’s capacity to regenerate the resource. So, for example, we overgraze land, deplete fish and game stocks, run down the water level in aquifers, or emit too much pollution into the environment. Generally speaking, common pool resource problems arise in situations where (i) individuals stand to benefit from using the resource to the greatest extent possible and (ii) the actions of any one individual have a negligible impact on the resource, but (iii) the actions of every individual taken together have a large impact. In these cases it’s often easy for an individual to see that the actions of the community as a whole are problematic, but because any individual’s decision to refrain from exploiting a resource is unlikely to make a difference by itself, individuals reasonably infer that they might as well exploit a resource for themselves while they can. As such, common pool resource problems are a species of collective action problem and are analogous in some ways to problems we’ve discussed in previous sections (e.g., how to ensure that members of a community are willing to police norms even when doing so is costly).