Ok “Ostracism is Community” sounds very Orwellian. It could very well be a mantra for a dictatorship based on isolating people or one of the lines from The Sphinx in Mystery Men.
But there is something to this mantra. The story starts with Stowe, as many stories do. In our discussions he had brought up mathematical based community identification algorithms. Now this is a question that has been plaguing graph theory specialists for a long time it turns out, and not something an astrophysicist could solve on the back of an envelope (bear in mind that in astronomy an order of magnitude is often seen as close enough).
So Stowe sent me a paper that proposed a new algorithm for the detection of communities in networks. Modularity is the key metric in this business and this paper is no exception. The quick explanation of modularity is that it is a measure of how a subnetwork is more tightlly knit than what randonmenss would indicate for the same group of nodes in that subnetwork. I will spare you the details of the paper as I my tenuous grasp of graph theory barely enabled me understand them myself, but suffice to say that small communities are very hard to delimit and that the calculation time required to perform this analysis is prohibitive for large networks.
What makes algorithmic community detection so difficult is a problem inherent in most algorithms: When do you make it stop? Mathematically, communities exist within networks, and in society the same is true. In todays nomenclature we often confuse networks with community. Where does the community end if it doesn’t take up the whole network? What is the maximum number of communities do we want to set in the network as the boundary condition?
The delimitation of communities is then a fundamental distinguishing factor between a community and a network, in fact it is a necessary condition of community. Communities are more closely knit, (as modularity calculations demonstrate) but additionally at least in real human communities, they also include goals or a a set of guiding principles, and the human boundary condition to community is a process of ex-communication or ostracism. You may ask: “How can something as vile and hurtful as ostracism be a part of something as inclusive and nurturing as community”?
In fact it is the ostracism that is making the community nurturing, because without ostracism the bounds of trust that are needed in communities are broken by the possible disruptive elements that may operate within that community. The community’s only answer to this is to expel the elements which break either the guiding principles of the community or injure the bonds of trust that enable it to take action.
The very word ostracism comes from an actual community that regurlarly kicked people out. The first recoded democracy in history in fact, Athens. Every year Athenians had a secret vote on one citizen they would chose to expel. They wrote the names of people they wanted to exclude on pieces of broken pottery called ostricon.
The Athenian who received the most “votes” was then kicked out of Athens or ostracized. For instance this Ostricon has the name of the Athenian statesman Cimon written on it. It’s kinda like voter recall but for everyone.
It sucks when the cool kids don’t want to hang out with you, I know (Astrophysicists are rarely part of the cool kid crowd in high school). Ostracism hurts when it happens, but everyone amongst us has told a troll to leave the discussion on a forum or thread, (Mr. Troll you know who you are). We have all stopped inviting the party guest who has to be right all night, diverges every discussion, starts fights and pisses every other guest off. We have excluded the carnivore at the vegetarian pot luck, the swing dancer at a tango night, or my favorite, the speed metal bassist in a country band. We have all done it, because we all cherish our communities and the goals they aim to achieve.