Not that I can see. He did use a lot of idioms and metaphors, though.
Try this question for examples of idioms.
its about having a dream is special thank you for your time
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"Idioms for Being Afraid", "Idioms for Being Angry", "Idioms for Being Happy" are some examples of idioms found in the book "Found" by Margaret Peterson Haddix.
It is both inductive and deductive. There are examples of both in his speech.
Check out this question for idiom examples.
"this hemisphere intends to remain the mast of his home."
When the English language developed. People have always used idioms and slang in their speech.
Americans love speech. Since we founded the country, we have loved speech-making and the sound of words. Americans just like using idioms and slang to make speech more colorful and interesting.
Authors use idioms the same way everybody else does -- by peppering their speech (writing) with colorful phrases!
Is martin's speech "I have a dream" persuasive speech?