A great speech doesn't speak only to the audience at hand, even if that audience numbers in the billions and engulfs the globe. A great speech also speaks to the past.

For a better appreciation of Obama's address, we've highlighted passages in which the president seemed to be not just speaking to us, but also echoing those who have gone before. Instead of quoting a great many famous documents directly and frequently, Obama chose instead to touch upon them gently and gracefully.

"My fellow citizens" "Not my fellow Americans. That was the key here. He's playing up citizenship," said Bruce Buchanan, University of Texas government professor and author of "The Citizen's Presidency." "That was a novelty. It's almost universally 'My fellow Americans,' in modern times at least." In a speech that sounds the call to citizenship loudly, Obama returns to the word explicitly in his conclusion, saying that "giving our all to a difficult task" is "the price and the promise of citizenship."

"still waters of peace"
This phrase recalls the first two lines in the King James translation of Psalm 23: "The Lord is my shepherd, I shall not want. He maketh me to lie down in green pastures: He leadeth me beside the still waters."

"set aside childish things"
This is a reference to the lines in Paul's First Letter to the Corinthians (13:11): "When I was a child, I used to talk as a child, think as a child, reason as a child; when I became a man, I put aside childish things." Stephen McKenna, chairman of the media studies department at Catholic University, said: "It's also a reference to his own victory speech, where he talked about the need to put away the 'partisanship, pettiness and immaturity that has poisoned our politics for so long.'."

"our better history"
This phrase echoes the concluding phrase of Abraham Lincoln's first inaugural address: "The mystic chords of memory, stretching from every battlefield and patriot grave to every living heart and hearthstone all over this broad land, will yet swell the chorus of the Union, when again touched, as surely they will be, by the better angels of our nature."

"their full measure of happiness"
An echo of the last line of the Gettysburg Address, in which Lincoln wrote, "It is rather for us to be here dedicated to the great task remaining before us--that from these honored dead we take increased devotion to that cause for which they gave the last full measure of devotion."

"Concord and Gettysburg, Normandy and Khe Sahn"
The Battle of Concord (April 19, 1775) was part of the first military engagement of the Revolutionary War. The Union victory at Gettysburg (July 1-3, 1863) was the turning point in the Civil War. The invasion of Normandy by Allied troops (June 6, 1944) was a turning point in World War II. The siege of U.S. troops at Khe Sahn (Jan. 21 to April 8, 1968) was one of the bloodiest battles in the Vietnam War.

"This is the journey we continue today."
The word "journey" is more momentous and historically inflected than a flat, ordinary word such as "trip." Yet it isn't as pretentious or stuffy-sounding as "voyage" or "odyssey." It echoes proverbs such as "A journey of a thousand miles must begin with a single step."

"Our workers are no less productive than when this crisis began."
While emphasizing the nation's strengths despite its economic travails, Obama echoes one of the central themes of Franklin Delano Roosevelt's first inaugural address, arguing that the country has all it needs to renew prosperity, except for leadership and revived confidence. Roosevelt, speaking to a cold March audience in the midst of the 1933 banking crisis, similarly said, "Our crises come from no failure of substance. ... Plenty is at our doorstep, but a generous use of it languishes in the very sight of the supply."

"pick ourselves up, dust ourselves off."
This is an allusion to lines in the song, "Pick Yourself Up" (music by Jerome Kern, lyrics by Dorothy Fields), sung in the Depression-era movie "Swing Time" by Fred Astaire and Ginger Rogers: "Nothing's impossible, I have found./For when my chin is on the ground,/I pick myself up, dust myself off,/Start all over again."