Martin Luther King's speech "I Have a Dream," an address he gave at the March on Washington for Jobs and Freedom on August 28, 1963, the largest civil rights gathering in American history, has long been studied as a masterful exercise in rhetoric and argument. King's appeal to reason and emotion combine to create a convincing argument that civil rights and freedom for Blacks in the United States is long overdue. Among the powerful rhetorical tools in the speech are economic and historical allusions that make more concrete the arguments he makes.
Given the make-up of his audience both on the Mall in Washington and listening on the radio, which includes significant numbers of the white middle-class, King makes an allusion that his audience, especially (but not only) whites, would immediately understand:
. . . America has given the Negro people a bad check, a check which has come back marked "insufficient funds". . . .
Many within his audience would have immediately understood the parallel between America's figurative "bad check" for freedom and a check returned by their bank for insufficient funds. King's allusion moves the abstract nature of America's failure into the concrete realm of the American banking system, a reality that many listeners would have experienced or at least understood.
From a rhetorical standpoint, perhaps King's most powerful series of allusions is in his vision of a truly free America, and he provides a verbal tour of the United States beginning with, "And so let freedom ring from the prodigious mountain tops of New Hampshire," and moving geographically east to west, encompassing the United States. In this section, he makes two allusions that his audience would have understood clearly as particularly important to the struggle for civil rights:
But not only that: Let freedom ring from Stone Mountain of Georgia. Let freedom ring from Lookout Mountain of Tennessee.
Here, he mentions an icon of the segregationist South and the Confederacy--Stone Mountain--a monument near Atlanta, Georgia, containing the bas-relief sculptures of Jefferson Davis, Robert E. Lee, and Stonewall Jackson. It stands today, as it did in 1963, as a symbol of the oppression from which Blacks are still seeking to escape. King's reference to Lookout Mountain is to a battle during the Civil War, one hundred years before King's speech, in which the Union Army defeated Confederate forces. King uses a Confederate icon, Stone Mountain, and a Federal victory, Lookout Mountain, as allusions to a war that was fought and won to free Blacks almost a hundred years before his speech.
King's allusions, then, allow him to touch intellectual and emotional points of contact within his audience to enhance the force of his overall argument--that freedom for Blacks is long overdue. By alluding especially to Stone Mountain and Lookout Mountain, King makes the point that the war to free Blacks was fought a long time ago and that it is now time for freedom to pay its dividends.