What rhetorical device does Dr. King use at the beginning of the excerpt? What is its purpose?

Martin Luther King, Jr. made many speeches over the course of his life. However, his most famous speech, the so-called "I Have A Dream" speech, is dominated by one particular rhetorical device: anaphora.

Anaphora is a type of parallelism in which a phrase is repeated at the beginning of several lines. In this speech, the phrase "I have a dream ... " is repeated, as King enumerates the various dreams he has for African American people. This ...