Their wooden plows differed little from those used at the time of the Norman Conquest. Livestock foraged for themselves, so they bred unselectively and their manure did not accumulate for fertilizer. (p.35)he is basically making an argument of une longue durée with respect to agricultural technique. Similarly, when Howe writes
Neither Alexander the Great nor Benjamin Franklin (America’s first postmaster general) two thousand years later knew anything faster than a galloping horse. (p.1)he is making a transportation-related observation, pointing out une longue durée, with respect to the speed limit of conveyance.
In the general case, a statement of longue durée appears as a form of universal quantification for a specific temporal range, where a single counter example can bring down the rule. But despite the fact that this is not logically impossible, we are willing to accept the veridity of these longues durées by virtue of the fact that they seem eminently plausible.
Upon introspection into potential sources of such certainty, I find the vague notion, that if a better plow or a faster mode of conveyance had become possible, we would have heard. It would have changed the world around. We imagine that it would have provided a general with a superior striking force, or a king with an agricultural edge, that would have been exploited.
If we consider the context of the study of the species in North America, were naturalists were constantly looking for new exemplars and gathering the specimens that they encountered, it is equally possible to make statements about the range of species, because if they were found elsewhere, they would have communicated that information.
It is the pressure of such an interest in gathering information that allows us to accept universal quantification in these cases.