In his Inaugural Address in January, 1961, President John F. Kennedy used several literary devices to make the speech impactful. Some are as follows.
A paradox is a statement that seems to be, at first glance...
...self-contradictory or opposed to common sense but upon closer inspection contains some degree of truth or validity.
Kennedy points out how powerful the world is, but that it has two very different sides.
...man holds in his mortal hands the power to abolish all forms of human poverty and all forms of human life.
Symbolism is also used with reference to a torch, symbolic of passion or dedication, used in this case with the passing of a torch that represents the passing on of responsibility.
Let the word go forth from this time and place, to friend and foe alike, that the torch has been passed to a new generation of Americans…
There is the sense of carrying a torch—a light ignited and burning without interruption—as was done in the Ancient Greek games, based upon the Olympic tradition which began in 1936—carried on still today: with a perpetual fire. This is the symbolic meaning that Kennedy refers to—that the quest for freedom, in the form of the ever-burning torch, has been handed down to a new generation.
Structural repetition is used in this address as well. In this sense, it is a poetic device that the appeals to the listening audience, tuning in to the list of things the United States is willing to do to assure liberty. Note the repetitive use of the word "any" and the repeated structure of each phrase that is given:
Let every nation know, whether it wishes us well or ill, that we shall pay any price, bear any burden, meet any hardship, support any friend, oppose any foe, in order to assure the survival and the success of liberty.
We see repetition used again, to drive the President's points home in the paragraphs that begin with "Let both sides…" and "To those…"
A wonderful metaphor compares the actions of tyranny to keeping company with a tiger:
...in the past, those who foolishly sought power by riding the back of the tiger ended up inside.
Another metaphor is used in comparing the oppression of poverty to chains that hold one prisoner:
...to assist free men and free governments in casting off the chains of poverty.
Finally, there is also the Greek "peripeteia," defined as a change or "reversal of circumstances." Generally used with regard to literature, it is known in English as "peripety."
Aristotle defines it as "a change by which the action veers round to its opposite…"
In President Kennedy's Inaugural Address, we see this after he lists pledge of support by the United States to allies, new governments, people in villages worldwide, and even the United Nations. However—and this is the reversal—the President now makes a "request" of those who would "make themselves our adversary." The tone of the speech changes as Kennedy sends out an implied warning—these adversaries should look toward peace before something terrible takes place (note: the use of "science" alludes to the "deadly atom"—nuclear weapons)...
...before the dark powers of destruction unleashed by science engulf all humanity in planned or accidental self-destruction.
The President says that we "dare not tempt them with weakness," for if other powers perceive the United States as weak, the country becomes a target. He says that only when the U.S. has arms that will dissuade others from attacking, will it have no need to use them.