For three hundred years modern epistemology assumed that knowledge is like a building, and that at its base lies a storey resting on nothing else — sense experience. A report such as "I am now seeing a red patch" was held to be independent of interpretation, theory, and language; self-certifying, and load-bearing for everything above it.

In three lectures at the University of London in 1956, Wilfrid Sellars named this the "Myth of the Given" and showed it collapsing under a dilemma. If experience really is raw, non-conceptual data, it can justify nothing — justification is a relation between propositions, not a matter of being struck by something. But if experience is conceptual enough to justify anything, then it is already inside language and concepts; it is neither raw nor merely given. In his famous formulation, in characterising a state as knowing we are not giving an empirical description of it; we are placing it "in the logical space of reasons, of justifying and being able to justify what one says."

This is a rejection of foundationalism, not of empiricism. Sellars went on defending empiricism; he denied only that knowledge has a ground floor, holding that the conceptual framework is tested as a whole. The "Myth of Jones" in the second half of the text makes the case from the other direction: thoughts and sense impressions could have been introduced to a community as unobservable but explanatory theoretical posits — so the privacy of inner life is an achievement of language, not its precondition.

Together with Quine's 1951 assault on the analytic–synthetic distinction, the essay ended foundationalism in analytic epistemology. Its influence ran through Sellars's students and readers: Rorty, and his Pittsburgh successors McDowell and Brandom. It is a difficult text; in Rorty's phrase, it did what few books in philosophy manage — not solving a problem but making people stop asking it.