The fallacy of judging past societies, actions, or norms by the standards of the present, or conversely, of justifying outdated, harmful practices by arguing "that was normal at the
time." In its dismissive form, it's used to invalidate modern
moral critiques of historical figures by claiming a lack of historical
context. More perniciously, it's used to defend the persistence of antiquated injustices by appealing to their historical commonality.
Example: Defending a founding
father's slaveholding by saying, "It was normal then, you can't judge him," commits the Historical Normality
Bias. It uses historical descriptivism ("it was common") to avoid moral judgment, implying that collective moral
failure excuses individual participation in atrocity.