(Cross-Posted in comments at Public Reason)

Jason Brennan of Brown University with an interesting take on the implications of Condorcet Jury Theorem:

So, if you defend democracy using the standard formulation of Condorcet’s Jury Theorem, it seems that you should think having 120 million Americans vote is kind of a waste of time. It would be far better just to have a small number of people vote and have everyone else go about their day. 119,899,999 of these people are just adding unnecessary accuracy to an already impressively accurate machine. They should go do something else instead. We just don’t need mass democracy. It doesn’t do us that much additional good. The first 100 thousand voters contribute more than the next 100 billion. Etc.

What Brennan has done is to calculate the diminishing returns for every nth vote in a democratic election until the additional accuracy in the population becomes too small to possibly be important.  However, one can still believe in jury theory and full participation.  Here’s why:

1. Brennan’s argument assumes every citizen is a .51 chance of being correct

2.  Many people are worse than a .51 chance due to ideological commitments, selective experiences, psychological frailties, etc.  

3.  Since we cannot know how many people are worse than a coin flip, and attempting to discern them would be unwise, why not just go overkill and let anyone votes who wants to?

On the other hand, I wonder what it would do to public campaigning and the tenor of political arguments if we did just select 200,000 people at random to vote. It would be a way to possibly re-orient politics to a general good and away from “base-rallying” measures. If there is not much likelihood that “get out the vote” will turn elections, the median voterin election  would more likely be close to the actual median voter, rather than a more movable object.