From William Hazlitt's essay *On the Ignorance of the Learned* (1821). Select the word that fits the blank. "Learning is, in too many cases, but a ______ to common sense; a substitute for true knowledge."

The second clause — *a substitute for true knowledge* — tells you Hazlitt's verdict on learning is **negative**. The first half must therefore name learning as something that gets in the way of, or substitutes for, common sense. *A foil to common sense* uses *foil* in its older sense: something that frustrates, defeats, or thwarts. (Later English narrowed *foil* to the literary sense of *a contrast that sets off another's qualities*, but Hazlitt's nineteenth-century usage is closer to *check* or *opposite*.) - "Tribute," "complement," and "guide" all assume learning *helps* common sense — the opposite of what Hazlitt is arguing. The doubling "a foil... a substitute for true knowledge" — two phrases joined by a semicolon, both saying learning *displaces* the real thing — is the load-bearing parallel that picks out the right answer.