Like James Buchanan, Jean-Jacques Rousseau, and many others before me, I invoke the “unanimity” condition whenever talking about social welfare (aka “the Greater Good”). The reason for this is simple: only through unanimous agreement can something truly be said to be for the greater good; that it improves social welfare.
Welfare economists (and others) will call me crazy for such a claim. “Of course that’s not true!” they say. “Simply look at the benefits the beneficiaries get, the costs the payers pay, and if the benefit is higher than the cost, then it increases social welfare.” This kind of cost-benefit analysis is important, I’ll grant that, but for the individual, not society as a whole. Extrapolating to the societal, or collective, level gets messy. The reason why is simple: valuation of costs and benefits are subjective. For any given individual, the valuation of the benefit of Good X is likely to be different from the valuation of the cost of Good X. Aggregating those valuations gets very very tricky and it ultimately leads to judgement calls by the analyst/policy maker.
If we want to make the claim that a collective action benefits the greater good, and we want to be able to say this positively and not normatively (that is, to eliminate judgement calls), then we need to apply the same standards as at the individual level, the most important of which being unanimity. In an individual action, all parties agree to interact; if there is no unanimous agreement, the interaction does not take place. If one disagrees, then we can conclude he does not stand to benefit from the interaction. Extrapolating this to collective action (that is, more than two people interacting), then the only way to positively claim the action benefits the group as a whole is if it is chosen unanimously.
At this point, I provide only assertions and light reasoning. An upcoming blog post will go much more in depth and I will attempt to prove my assertion, using the reasoning of James Buchanan and Gordon Tullock. However, this post is long enough as it is and I will bore the reader no further.