In the play, the character of the logician explains that a syllogism "consists of a main proposition, a secondary one and a conclusion." The logician absurdly illustrates this concept by stating that anything with four paws is a cat—which means, as the old gentleman realizes, that a dog could be defined as a cat. The logician's syllogisms show the limitations of logic and reveal how false propositions can lead to false conclusions. The play examines how logic can be twisted and exploited to recruit people to irrational causes, such as transforming themselves into destructive rhinoceros, which are Ionesco's symbol for fascists. The play mocks the way people sit and around and debate philosophical trivia while the world is falling into crisis.

Characters in the play include Berenger, Jean, Daisy, the logician, Botard, Papillon, Dudard, Mr. and Mrs. Beouf, and a number of townspeople, such as the old gentleman, the grocer and his wife, the cafe owner, the waitress, and the housewife. The many clichés and syllogisms which the characters repeat over and over symbolize the way they have stopped thinking for themselves, which makes them susceptible to being transformed into rhinos. The only character who is saved from becoming a rhino is Berenger. He is an alienated slacker, too removed from the culture he is part of to be sucked into its pathologies.