On field trips in Jerusalem, I often show students certain marks on the facades of shops and houses dating to the Crusader period. Incised in the form of a triangular shield containing the inverted letter "T", they are believed to have been made with the intention of identifying property belonging to the Templars, and to ensure that the tenants, shopkeepers or residents, paid to the order the taxes or rents that were due. There are also insignia for other property owners.
On one occasion a shopkeeper whose shop was adjacent to one of these marks, took offence at my explanation, and with absolute confidence informed us that these shops were, and always had been owned by Muslims, and that in fact, the mark in question had been made by Saladin. The next time I had an occasion to point out the sign to another group of students, I found that it had been neatly covered over with a layer of cement. Clearly, the shopkeeper did not intend to allow me to continue misinforming my students by making such preposterous statements.
I am not sure just how this enlightened shopkeeper knew that it was none other than Saladin himself who had incised the mark on this spot, but this did lead me to wonder about the assurance with which I have often accepted information obtained from my own observations and from the observation of others. How can I be certain that my understanding is any more reliable than that of the shopkeeper? Certainly, much of what we regard as fact is in reality assumption, hopefully reasonable, but assumption nonetheless. Were it possible to travel back by time machine, and actually walk around twelfth century Jerusalem, I wonder how much of what we believe to be, might prove to be complete nonsense.
I learnt to drop the words "I have no doubt…" from my own lexicon several years ago when excavating at a Templar castle north of the Sea of Galilee. On one occasion, having read a very detailed medieval description of the castle's deep, stone-lined well, into which, when the castle was taken, the bodies of knights and horses had been thrown, we came upon a round, stone-lined structure, surrounded by skeletons of men and horses. It was quite clear to me that this was the well we had been looking for. However, shortly after we began to excavate it we hit a solid, ash-covered floor, and it became apparent that this was in fact not the well but a bakery oven. Archaeology is a very good cure for the overconfident.
Worse, perhaps, than being overly certain when presenting postulations to students, is being so to reporters. Some people in that profession are very reliable, but there are others, who, if it makes for a good tale, will quite happily turn conjectures into statements of fact. A colleague of mine, if I recall the story correctly, excavated the remains of a large animal at a certain position in a castle, and human remains at another location some distance away. Someone had suggested to him that the animal he had exposed might be a horse. A visiting reporter, hearing this information, published an article under banner headlines, stating that the archaeologist had found the remains of a knight riding a horse - no matter that the two were located about fifty metres apart, that the "horse" turned out to be a pig, that the human, although indeed a human, was no knight but probably a stone robber, and that he had lived several hundred years later than his "horse"… Why spoil a perfectly good story with tedious facts?