But maybe voting is neither commons nor market. Perhaps, instead, it’s combat. Relatively gentle, of course. Rather than rifles and bayonets, essentially there’s just a show of hands. But the nature of the duty may be similar, because what Brennan’s model omits is that sometimes, in an election, democracy itself is in danger. If a soldier were to calculate his personal value to the campaign that his army is engaged in, he could easily conclude that the cost of showing up at the front isn’t worth it, even if he factors in the chance of being caught and punished for desertion. The trouble is that it’s impossible to know in advance of a battle which side will prevail, let alone by how great a margin, especially if morale itself is a variable. The lack of certainty about the future makes a hash of merely prudential calculation. It’s said that most soldiers worry more about letting down the fellow-soldiers in their unit than about allegiance to an entity as abstract as the nation, and maybe voters, too, feel their duty most acutely toward friends and family who share their idea of where the country needs to go.