The double defection outcome is undesirable because they each serve 2 years. The double collusion outcome is desirable because they each serve 1 year. The other

The double defection outcome is undesirable because they each serve 2 years. The double collusion outcome is desirable because they each serve 1 year. The other two options are more desirable for each prisoner, but would never happen. Either they can't trust each other and both defect, or they can trust each other and both collude. Likewise, taxes paid for selfish reasons cannot necessarily be optional, as you suggested. If the tax is optional, you cannot trust your fellow citizens to pay it, and therefore you won't pay it. But a compulsory tax removes that distrust. My point is mainly that you can be selfishly motivated but still require consensus. The author supports Scandinavian policies not (entirely) because it helps everyone else, but because it helps themselves. Yet they still recognize that everyone must participate for it to help anyone at all. I'm not trying to make any claims about how efficient a socialist system is. Simply arguing against the point you made about paying optional taxes.