 To illustrate these concepts, consider a case in which all witnesses report exactly the same thing, e.g., that John was at the crime scene. That would be a paradigm case of a (highly) coherent set of reports. Now contrast this situation with one in which only one witness reports this. That would be a situation which would intuitively not qualify as coherent. Indeed, it does not even seem meaningful to apply the concept of coherence to a case of just one report (except in the trivial sense in which everything coheres with itself). Letting \(A\) be the proposition “John was at the crime scene”, and \(E_1 ,\ldots ,E_n\) the corresponding reports, this intuitive difference can be represented as the difference between two testimonial systems: \(S = \{\langle E_1,A\rangle ,\ldots ,\langle E_n ,A\rangle \}\) and \(S' = \{\langle E_1,A\rangle \}\). If, by contrast, the entities to which coherence applies are represented as simple unstructured sets, the sets of testimonies in question would be given the same formal representation in terms of the set having \(A\) as its sole member.