This is not the point of this thread. And I am not a libertarian. But there is reason to believe that in most arenas, self-interest does lead to the emergence of something close to an optimum (admittedly an optimum defined with a weird notion of optimality). The result breaks down when prices don't reflect actual costs (as in, the social cost of a knitted sweater can be argued to be exactly the same as the market cost, whereas the social cost of oil extracted from the Arctic can be argued to be higher than it's market cost). The problem is what to do there. There are reasons to believe that governments won't behave optimally (they typically would have huge information costs, even if they had the best intentions), and reasons to believe that businesses wouldn't behave socially optimally (duh). So neither side is a given, and perhaps the skeptical answer would be that we are very limited in how optimal our social arrangements will be. This is obviously my own position, because I R moar SkAptik than u.