Kevin Quinn makes an excellent point about group decision-making; 
there is an expectation of INTERDEPENDENT decision-making in a 
democracy that I seldom find expressed in the econ models about it. 
That is, it is possible for a group to come together to deal with a 
problem, each having their own idea of what the solution ought to be, 
and for them to DISCUSS each other's ideas until they come up with 
a solution that is acceptable to most (or all, in the Quaker model); 
we can consciously realize that we are working for a JOINT solution.  
This is, of course, an ideal type -- but economic theory is all about 
ideal types.   
     My awkward phrasing about the "common will" was to distinguish  
between the situation where a politician is voted into office having 
stated during the campaign that he/she intends to devote more spending 
to education, or to change the educational system in some way, and then 
the politician proceeds to do it.  Now, economists may model this as 
"rent-seeking", talking about which families benefit and which ones don't. 
But what is missing is the possibility that the electorate (or the 
majority) as a whole was quite willing for that to happen.  That is, I 
know that my tax money will benefit the welfare child across town, and 
that's fine with me.  Then we will be arguing about the minority -- 
and in a democracy, there is supposed to be a certain amount of giving 
and taking on these things -- not simply "winning" and "losing". 
     Second, you have the situation where it is guinely a public good. 
In a democracy, it could be argued, it is in EVERYONE'S interest that 
the electorate be sufficiently well educated to be able to vote 
sensibly (that is, everyone except a potential demagogue.)  If the 
public in general has expresed a long-standing, multigenerational 
preference for democracy over dictatorship, then I am not inclined to 
view this simply as a tradeoff between equal groups.   
     Third, it is hypothesized, and has been supported by some studies, 
that a well-educated populace is better able to respond to, and create, 
economic growth.  It could be argued that if our goal is ecoomic growth, 
it is at least as sensible to improve the educational system as to 
give tax breaks to income from capital gains.   
     Have you not benefited from the invention of the polio vaccine, 
for example?  It is very difficult to measure the precise range of the 
effects of education.   
     But -- how about the southern California defense mega-corporation 
that makes sure to have executives in decision-making positions in the 
federal government, not out of a general social consensus, from  
discussion or voting, but out of an open and crass desire to keep those 
defense contracts coming their way?  Or the local contractors where 
I live, who funnel income into the hands of the local county government 
to get zoning allocations their way -- rational rent-seeking, for sure, 
but of a very diferent NATURE than educational funcing. 
     This is what concerns me -- a nit-picking, chipping away at 
distinctions, until all outcomes are the same -- so no differences 
really matter -- so there is no legitimate basis for discussion or 
persuasion -- and eventually it will come down to raw power and who 
possesses it.  If all government is coercion, but some government is 
necessary -- how are we to choose what is necessary? 
     If our model tells us it's all about different groups jockeying for 
crass increments to income -- well, then, we're all alike, eh?  Jane 
Addams and Spiro Agnew.  Martin Luther King and the Shah of Iran. 
     To me, the theory of rent-seeking speaks to something very 
particular that is DESTRUCTIVE of the community, wasteful of resources. 
A certainly morality is essdential to the smooth running of both 
markets and government -- lying, cheating, stealing can be mighty 
expoensive if rampant.  A strange world we are in where we hyperfocus 
on "moral hazard" when a coalminer has disability insurance, or  
whether a worker is putting up as much "effort" as he/she can -- 
but anyting goes in government -- it's all equal.   
     Apollogies if this is muddled; I'm having a brain fog day. 
     -- Mary Schweitzer