Diderot’s definition of facts, as presented in the original Encyclopédie:
Facts: You can divide facts into three types: divine, natural and man made. The first belong to theology, the second to philosophy and the others to actual history. All three are open to question.
…from An Unconscious Civilization1
It’s the last line that I find most significant; its understood within the context of philosophy, but in the case of the others, they often appear sacrosanct (yes history, too).