 The wording of Lewis’ definition and the use he makes of the indication relation in the definitory clauses for common knowledge, suggest that Lewis is careful to distinguish indication and material implication. Cubitt and Sugden (2003) incorporate such distinction in their formal reconstruction. Paired with their interpretation of “\(i\) has reason to believe \(x\)” as “\(x\) is yielded by some logic of reasoning that \(i\) endorses,” we have that, if \(A \indi x,\) then \(i\)’s reason to believe \(A\) provides \(i\) with reason to believe \(x\) as well. Given that Lewis does want to endow agents with deductive reasoning, (Cubitt and Sugden 2003) list the following axioms, claiming that they capture the desired properties of indication. For all agents \(i, j,\) with \(\mathbf{R}_i A\) standing for “agent \(i\) has reason to believe A”, we have