‘One of the difficulties facing the archaeologist when trying to use the evidence of ancient writers is to know when that writer (historian or otherwise) is relating fact, and when he is merely involved with “topoi” – the stock literary descriptions or situations inseparable from history as rhetoric’.
In defining this problem, J.C. Mann is thinking specifically about Tacitus' references to Britain. He presents a constructive warning to those who rely too confidently on literary sources, yet in one sense his statement is also misleading, for he elevates ‘fact’, regarding references that are ‘merely’ topoi as inferior, not to say deceptive. This distinction is indeed necessary when we are compiling information for a military or political history; but in the study of Roman Britain too little attention has been paid to the historical value of sources in their own right, as evidence for Roman culture and society rather than sources as such.