Abstract
Solving the collective action problem is to understand how people decide to act together for the common good when individual rationality would lead to non-cooperative selfish behaviour. Two important features that can foster collective action are achieving common knowledge about the problem faced and the existence of a shared cooperative ethos. Based on the work of Ober, who argued that the success of classical Athens was the result of its shared commitments, social values and specific procedural rules, we define a probabilistic model in Markov Logic of a specific prosecution against an Athenian trader who neglected to contribute to the city when it was in a crisis. In order to join together for a common good, our model focuses on a decision-making approach based on reasoning about common knowledge. For example, knowledge about the ethos of the court towards convicting traitors can be seen as common knowledge gained from public monuments recording these verdicts. We expect that our computational model of this case study can be generalised to other problems of reasoning about collective action based on common knowledge in future work.