 Definition 2.6  Given a set of agents \(N\) and a proposition \(A' \subseteq \Omega\), the agents of \(N\) are symmetric reasoners with respect to \(A' (or A'\)-symmetric reasoners) iff, for each \(i, j \in N\) and for any proposition \(E \subseteq \Omega\), if \(\mathbf{K}_i (A') \subseteq \mathbf{K}_i (E)\) and \(\mathbf{K}_i (A') \subseteq \mathbf{K}_i\mathbf{K}_j(A')\), then \(\mathbf{K}_i (A') \subseteq  \mathbf{K}_i\mathbf{K}_j(E)\).[13] 