Book excerpt: A proposition of contemporary economics and political science is that it would be an exercise of reason, not a failure of it, not to contribute to a collective project if the contribution is negligible, but to benefit from it nonetheless.Tuck makes careful distinctions between the prisone's dilemma problem, threshold phenomena such as voting, and free riding. He analyzes the notion of negligibility, and shows some of the logical difficulties in the idea - and how the ancient paradox of the sorites illustrates the difficulties.