It seems to Searle that Hume and Nietzsche were probably the first philosophers to appreciate, respectively, the centrality and radical contingency of the Background. "Nietzsche saw, with anxiety, that the Background does not have to be the way it is." Searle also thinks that a Background appears in the ideas of other modern thinkers: as the river-bed/substratum of Wittgenstein's On Certainty ("the work of the later Wittgenstein is in large part about the Background, especially "On Certainty"") and Pierre Bourdieu's "habitus".