In a broad sense, the meaning of dichotomy implies a division of a group, a phenomenon, or an object into two parts or sub-groups, which are characterized by being opposite, contradictory, and mutually exclusive. This term is widely used in different niches, including philosophy, math, and linguistics. In theology, a dichotomy implies the belief in the presence of both human body and soul. In sociology, a dichotomy can be used to describe the division of social roles that belong to men and women. A dichotomy often stands beside a contrasting term – trichotomy, which denotes a three-way division and classification.

The definition of a dichotomy as a literary device has a connection to the general meaning of the word, even though the linguistic definition is more narrow and specific. Thus, in literature, a dichotomy is the way to present and express contrast or division between two concepts, ideas, phenomena, or even characters. It is a literary tool, which allows the author to describe two opposite concepts, contrasting ideas, or even competing objects and matters.

The word “dichotomy” originates from the Greek “dichotomia,” which can be translated as “being cut in half” and consists of two parts: “dicha” meaning “in two” and “temnein” meaning “to cut.” Its origin dates far back to 1600-1610, which means scholars used it to describe contrasting matters in philosophy, mathematics, social studies, literature, and science many years ago. 
The synonyms of “dichotomy” are: being twofold, contradiction, and duality. They don’t coincide fully with the meaning of dichotomy but can be used to understand the definition of this literary tool better.

The term that is closely connected with a dichotomy and is being used as often as this literary technique is called a false dichotomy. It is often confused with the original term, even though it has a different meaning. A false dichotomy implies an unfairly presented situation that suggests only two possible choices, when, in reality, there are more options available. It is often structured with the “either + or” pattern. For example, “You are either with us or against us,” which creates a dilemma for the subject and limits one in the number of possible choices. In reality, the subject has more possibilities than simply being “with them” or “against them.” 

So, unlike its previously mentioned false version, a dichotomy doesn’t limit the objects or ideas to only two; it allows to represent them as the contrasting and opposite ones.  

A dichotomy, being an important and effective literary tool, allows the author to quickly and easily identify objects or phenomena. By placing two issues in contraposition, the author helps the reader understand them better by comparing and contrasting them, paying attention to the features that one of them has and the other one lacks, and vice versa.  

The brightest and the most common examples of a dichotomy in literature are peace and war, hatred and love, and, of course, evil and good. These classical comparisons and oppositions have taken their strong place in literature.

The authors started using a dichotomy hundreds of years ago to aggravate the feelings, worries, and internal experiences of their characters. One of the brightest examples lies in one of Shakespeare’s legendary tragedies – Macbeth. Here, a dichotomy is used a couple of times. It is applied when the main protagonist experiences the volatility between remaining an unconverted philosopher and becoming an actual murderer, a vigilante. He is also the embodiment of the dichotomy between existentialism and nihilism. Macbeth also represents the contrast between the orthodox values, humility, and obedience, and the faithless heroic morals.

Another example from the eternal classic is Hamlet and his dichotomy of action and inaction. The main character and his famous words “To be or not to be” show the most traditional example of a dichotomy and the contrast between deeds and words. 

While the previously mentioned examples display the internal experiences and struggles under certain circumstances, Robert Stevenson’s novel shows the dichotomy of the individual and his versatile nature. Jekyll and Hyde is one of the most obvious examples of a dichotomy, which represents the contrast between evil and good. Here this literary tool allows the author to explain the human nature more clearly.