 Another important contrast to draw is between the common good and a public good. In economic theory, a public good is a particular type of good that members of a community would not possess if they were each motivated only by their own  self-interest.[4]  Here is an example. Imagine that the residents in a town could enjoy a mosquito free summer if most every resident treats her lawn with a bug spray. The spray costs money, but every resident would be better off having paid for the spray and enjoying life without mosquitoes. If most every resident sprays her lawn, everyone in the town will enjoy the benefit, even those residents who do not spray their lawns. But there is no feasible way to exclude the nonsprayers from enjoying the benefit.