Chiasmus is the reversing the order of words in the second of two parallel phrases. This rhetorical device is also referred to as reverse parallelism, antimetabole or syntactical inversion.
In rhetoric, parallelism means giving two or more parts of the sentences a similar form so as to give the passage a definite pattern.
In the end, the true test is not the speeches a president delivers; it’s whether the president delivers on the speeches. - Hillary Clinton
People the world over have always been more impressed by the power of our example than by the example of our power. - President Bill Clinton
My job is not to represent Washington to you, but to represent you to Washington. - Barack Obama
Let us never negotiate out of fear, but let us never fear to negotiate. - President John Kennedy
If black men have no rights in the eyes of the white men, of course the whites can have none in the eyes of the blacks. - Frederick Douglass