Editors’ Note: Donald Kagan, Sterling Professor of Classics and History at Yale University and recipient of the National Humanities Medal (2002), retired in May. In forty-four years at the University, Professor Kagan has served in such varied capacities as Dean of Yale College, Master of Timothy Dwight College, and Director of Athletics. He has been a prolific author as well as a celebrated teacher; his four-volume history of the Peloponnesian War is widely considered to be among the twentieth century’s greatest works of classical scholarship. The following essay on liberal education is a revised version of the valedictory lecture he delivered on April 25 to a capacity audience in Sheffield-Sterling-Strathco ...