Final answer:
The rhetorical device prevalent in Martin Luther King Jr.'s "I Have a Dream" speech is anaphora, which is the repetition of a word or phrase at the beginning of successive clauses for emphasis and rhythm.
Step-by-step explanation:
The prevalent rhetorical device used in the passage from Martin Luther King Jr.'s "I Have a Dream" speech is anaphora. Anaphora is a rhetorical device in which a word or phrase is repeated at the beginning of successive clauses or sentences for emphasis and rhythm. In the iconic speech, King repeats the phrase "I have a dream" at the beginning of several statements, creating a powerful and poetic rhythm that emphasizes his vision for equality and justice.
The speech not only utilized anaphora but also included metaphors, which compare two things by stating they are the same, and the repeated reference to the dream works to create a sense of hope and unity in the audience. King's speech is a quintessential example of the effective use of rhetorical strategies that were influential during the Civil Rights Movement, as it inspired people to envision and work towards a future of racial harmony and equality.