Answer:
To show how metaphors can express complicated ideas
Step-by-step explanation:
The purpose of the writer is to show how the metaphor can be used to explain complicated ideas, as Martin Luther King did in his "Letter to Birmingham Jail".
Metaphors are a figure of speech very common in our day to day, present in all the textual genres (yes, including in scientific articles of all the areas). Thus, it is not only a rhetorical or poetic figure, an unnecessary ornament of the texts. Metaphors are a way of understanding, of explaining complex concepts and of saying about the world and of manifesting it in different ways: in language (through linguistic expressions), in images (movies, comics, commercials), in sounds, among others. The consistency with which we use certain metaphors leads scientists to propose that they are more than a mere figure of language, they are a figure of thought.