Q: Can you help me define rhetoric, flattery, and justice?
A: Some thoughts on language.
My view of all speech is shaped by J.L. Austin's book How to do Things with Words. In it, Austin makes the profound insight that speech is best understood not as the communication of facts or ideas, but as action. There's an entire field of linguistic philosophy called "speech-act theory" which is based around his insight. However, it's not new. It contains the basic framework of medieval nominalism, the school Luther was trained in, which provided the framework through which he made such profound observations about the power of the Word of God.
Rhetoric: Rhetoric is the art of doing things with words. You could think of a speaker as a soccer player who has specific aims and obstacles. His job is to make his team score and prevent the other team from scoring. He may take many different routes to get there, including passing the ball back toward his own defense or goalie, or deliberately kicking the ball out of bounds. The essence of every action, however, is to use creative ways to eventually put the ball where he wants it to go.
The same is true in speech, although the rules are less clear, and the effect of your words is not nearly as obvious as whether or not you kicked the ball the way you wanted to. Rhetoric is the study & use of the rules and techniques that will help you to make the words act how you want them to. Here is what Luther said of the composer Josquin des Pres: "He is the master of the notes. They must do as he wills; as for the other composers, they have to do as the notes will." The goal of the rhetor is to be a Josquin of words.
Flattery: Flattery is a form of cheap rhetoric. There is always more than one way of getting somewhere. If you want someone to come to an event, for example, you can tell them why you think they should come and try to make a compelling case for it, or you can appeal to their lower appetites, such as "there will be an open bar" and "gee, you're a swell guy who belongs at a great party." The latter one is flattery. It's not necessarily untrue or wrong, but it motivates from lower goals and should be avoided in most cases. BTW, the other side of the flattery coin is motivation through guilt, something preachers do too often.
Justice: Justice (in rhetoric) is when words line up with God's deepest plans for reality (truth in beauty). A just word not only achieves the aims of the speaker, but also glorifies God through nobility of expression, clarity of thought, and celebration of the good.