The term "liberal arts" usually conjures up one central idea; that is, effective liberal arts education as strong academic achievement. A second, less dominant, and frequently neglected notion regards effective liberal arts education as producing intellectual interests and habits that endure throughout adult life. The two ideas are complementary and not in opposition. But they are different. The dominant idea associates the liberal arts with a collection of academic subjects or disciplines, most often divided into three broad and overlapping groups. For example, they are labeled by the National Center for Education Statistics as humanities, social and behavioral sciences, and natural sciences. The second idea about the liberal arts tradition is that what begins as a required activity assessed just after instruction should become voluntary behavior engaged in for curiosity and pleasure. The ultimate agenda of the liberal arts is how a person lives his or her life--what that person is like as an adult and not merely as a youth at the time school graduation requirements have been met. The ultimate product of an effective liberal arts education is active reflection about serious ideas. Enduring intellectual interests are to be created and pursued long after required courses and examinations are over and done with. This essay explores both the academic achievement side of the liberal arts tradition and the enduring intellectual interests side as they have played out in American high schools. The author discusses three historical windows that further illuminate the interplay among ideas about the liberal arts. First is the work of Charles W. Eliot at the end of the nineteenth century which crystallized ideas about the content and purpose of modern high school academics. Second is the reaction against Eliot's work by the professional custodians of the rapidly expanding American high school. A third window is the role of elite higher education, especially in the first half of the twentieth century, as guardian and primary generator of the liberal arts tradition. Comments by Jeffrey Mirel and Richard J. Murnane are presented. (Contains 64 notes.)