In one of my earlier avatars, after Rama but before Kalki, I edited math textbooks and in the process learned three things from my interviews with thousands of mathematicians. First, mathematicians are cheap dates—statisticians order the oysters, mathematicians the soup. Second, mathematicians are lousy at judging the qualifications of the people they meet—my contacts regularly assumed that I had a PhD in math when my transcripts show that I took my last math class at Gardena High School in 1963. What math I know I picked up as an anthropologist, going native, might learn how to shrink heads. The third insight was more substantive. The secret reason math folks want to inflict calculus on so many undergraduates is not that very many people will ever integrate a function in anger but because passing calculus absolutely requires a student to finally learn algebra and, Woody Allen to the contrary, lots of people need that. By the same logic, if you really need to understand calculus, you need to take differential equations. And so on. The general rule is that it makes sense to take one more course than it makes any sense to take. Generalized still further, an analogous logic works in the Liberal Arts.
Literary criticism has a terrible reputation just now, and various pundits bewail the fact that all theory gets between the common reader and the various sacred texts. But commentary, whatever its intrinsic value, can serve to enforce the careful reading of books in the absence of snap quizzes. Though the notion of a virgin reading is simply incoherent on this side of the Moon, I suppose the very best readers can dispense with overt mediation if they are willing to fall in love with a text, and there really isn’t any substitute for memorizing poetry, but very few of us are in the situation of Abraham Lincoln puzzling out Shakespeare by the fireplace light. We need indirections to enforce our attention and, above all, to slow us down until we catch up with the text.