Having a vivid description can make your writing more persuasive. It sometimes hard for me to create vivid description because I admit that I don't have a big imagination but there's still that imagination remaining in my brain. If you're making unrealistic things come alive, you're actually asking your audience to see something you see or hear something you hear. I think that's an important thing to learn in order to persuade your audience.
I didn't know that "defining a term is the first step in a debate or disagreement." That phrase reeled me in. I guess it means that you have to define a word precisely or else someone will be responding you by a disagreement.