The repeating of a phrase in reverse order is known as an antimetabole – Roopa Banerjee
The sentence ‘Fair is foul and foul is fair’ hits a lyrical and rhetorical note because of the placement of words in 
reverse order. This repeating of a phrase in reverse order is known as an antimetabole.
Antimetabole is derived from the Greek words anti which means against or opposite and metabole i.e change. This literary device has been used since 450 BC, from the time of Greek philosopher Socrates. His famous quote: ‘Eat to live, not live to eat’ is one of the earliest examples of an antimetabole.
However merely reversing the meaning is not enough to create an antimetabole. The words and grammatical structure should also be swapped to contrast the meaning. American actress and comedienne Mae West’s memorable quote: “It’s not the men in my life; it’s the life in my men I’m worried about,” is a classic example of creating a contrast in meaning. Here, the words, rhythm, and grammatical structure in the second phrase are exactly similar to the first, but the meaning is the mirror opposite.
An essential component of an effective antimetabole is that it should have a logical premise. Reversing a phrase for the sake of it is not enough. If the first half of the antimetabole is relatable, the listener will be able to make sense of the second. Thus, “It is not about the years in your life, but about the life in your years that matter,” is logically and grammatically correct and conveys a message to readers.
This literary device is most popular with world leaders and politicians because antimetaboles are rhetorical, easy to remember, memorable and appeal to audiences. An oft-cited example is “Ask not what your country can do for you, but ask what you can do for your country,” by the late US President John F. Kennedy. Another popular example is Winston Churchill saying “It is not even the beginning of the end but is perhaps, the end of the beginning,” in his 1942 speech about the second battle of El Alamein.
Dr. Martin Luther King, renowned for his powerful oratory skills famously said, “Hate destroys a man’s sense of values and his objectivity. It causes him to describe the beautiful as ugly and the ugly as beautiful, and to confuse the true with the false and the false with the true.” In a more recent example, former US President Barack Obama said, “You stood up for America, now America must stand up for you” (2011).
Antimetaboles are also popular with advertising copywriters. For instance the tag line of Band Aid reads: “I am stuck on band-aid, because band-aid’s stuck on me”. Scuba diving enthusiasts would have often heard this from their instructors, “Plan your dive, dive your plan.” Other examples: “When the going gets tough, the tough get going” and “Fail to prepare and you prepare to fail”.
Literature abounds in antimetaboles. The legendary playwright William Shakespeare used it in many plays. “Fair is foul, and foul is fair” is from Macbeth and “Virtue that transgressed is but patch’d with sin, And sin that amends is but patch’d with virtue,” from Twelfth Night. The British poet John Keats wrote, “Beauty is truth, truth beauty, that is all ye need to know,” in his iconic poem Ode to a Grecian Urn. Children will be familiar with American children’s author Dr. Theodor Seuss’ lines “I meant what I said, and I said what I meant” from his book Horton Hatches the Egg.
In a good antimetabole, the entire argument is summed up in a short sentence. The reversal of phrases shifts emphasis to show what’s important. This can take the reader or listener by surprise as it mostly challenges a commonly held belief. Sometimes, however, antimetaboles can become somewhat corny, especially in jokes such as: “What is the difference between a crocodile and a baby? One makes its bed in a river and the other makes a river in its bed.”
To conclude, here’s a grammatical witticism which is an intelligent antimetabole: “A cat has claws at the end of its paws; a comma is a pause at the end of a clause.”
