I have been nibbling at the edge of Amartya Sen's book, COLLECTIVE CHOICE AND SOCIAL WELFARE in recent posts. Today I'd like to dive into the heart of it. But to do that, I have to start with Kenneth Arrow. Arrow is the author of the "impossibility theorem," the logical argument that there is no optimal way to make collective choices -- no voting system, in particular, that will not be open to devastating objections. Arrow's argument begins with premises about what is an acceptable, or unobjectionable. We want a system in which each of the five will be true: 1) The system can handle any level of pluralism in its inputs (universal domain). 2) The system does not produce paradoxical circles (in which a beats b, b beats c, and c beats a). This demand is known as ordering. 3) If all individuals in the society prefer x to y, then so does "society." The "weak Pareto principle." 4) The independence of irrelevant alternatives. The choice between x...