Historian: There is no direct evidence that timber was traded between the ancient nations of Poran and Nayal, but the fact that a law setting tariffs on timber imports from Poran was enacted during the third Nayalese dynasty does suggest that during that period a timber trade was conducted  Critic: Your reasoning is flawed
During its third dynasty, Nayal may well have imported timber from Poran, but certainly on today' s statute books there remain many laws regulating activities that were once common but in which people no longer engage
It identifies a general principle that the historian's reasoning violates.