 Impartiality  Suppose \(p,\ q\in \Omega\) are mutually incompatible and \(p\sim q\). Then if \(p\cup r\sim q\cup r\) for some \(r\) that is mutually incompatible with both \(p\) and \(q\) and is such that \(\neg(r\sim p)\), then \(p\cup r\sim q\cup r\) for every such \(r\).