Models and reality: the curious case of the absent abstention

We discuss two inter-related puzzling features of the literature on a priori voting power. First, the mathematical model used in virtually all this literature does not recognize abstention as an option distinct from both a 'yes' and a 'no' vote. Second, real-life decision rules of voting bodies---in particular the US legislature and the UN Security Council---are misrepresented as though they did not allow abstention as a tertium quid. We suggest that these misrepresentations may be examples of what philosophers of science call 'theory-laden observation'