In one of my exams yesterday, I had prepared for (well, kinda) and expected a question on Calvin because there had been one on every single past paper. But there wasn't, so I ended up blagging about confessionalisation from the point of view of game theory. This is a tidied up and shortened version of what I said...
Confessionalisation was a big feature of the Reformation, after the start. In 1528 (for example), there were lots and lots of different groups all across Europe, and all believing different things. You could go to London or Amsterdam or Munich or Venice and find lots of people who believed lots of different things. By 1650, that wasn't possible in the same way any more. The number of beliefs held had greatly decreased, and each region was much more homogenous.
I argued that it was an inevitable consequence of the view that religion could be legislated, and that different states could have different beliefs - the policy known as cuius regio, eius religio (each region, its own religion). If we assume (as a simplification) that there is only one issue, and it can be represented by your position on a line, then we have the following picture.
Points A and B represent the religious positions of two rulers, who are not on friendly terms. Ruler A will therefore suspect anyone to the right of him of being a sympathiser with B - they all appear to him to be in the same direction, so he will persecute everyone to his right. Ruler B, likewise, will persecute everyone to his left. This will lead to a polarisation of the centre - if they remain in the centre, they will be attacked by both the right and the left; the pressure on them greatly reduces whichever direction they travel in. Therefore the centre will largely disappear.
The second stage is that of consolidation. In this, the fairly large number of early positions consolidate over a long period of time into fewer positions. This is largely due to the influences of education, particularly of ministers and rulers, and the production of literature. If one fairly homogenous group produces large quantities of literature which become available in other areas, or if they have training facilities with such a good reputation that they attract people not just from within the group but from similar groups, they are likely to win "converts" to their cause, and to grow at the expense of those other groups. And the larger they get, the more significant this effect is. This is largely what happened with Calvinism. Due largely to better publishing and writing, and better training facilities (as well as better systematic theology and God blessing them), Calvinism grew rapidly at the expense of most of the other Protestant groupings, to the extent that the only major Protestant groups left by 1650 were Calvinists, Lutherans and Anglicans.
Of course, I simplify hugely. But it seems to work fairly well for a first order model. Apparently, though, historians aren't overly fond of this sort of thing, and I haven't heard of many people applying even very simple game theory like this to history... Never mind, it was a fun sort of idea, and I'm still a physicist in my methodology.