2,500 years ago, Aristotle argued that there are three ways that you can persuade anybody to change their mind. This is as true for business negotiations as it is for debate with your partner. It can be used for good, or for ill.
First, there is logos, which is sound reasoning and a clever argument. It's when you lay out your facts in a clear and sound way, and you hope the other person is rational enough to appreciate them.
Second, there is ethos, which is the character or credibility of the person speaking. For example, if a doctor is talking about medicine, or a teacher is talking about their subject, you are more likely to trust them than some random person on the street. Ethos is about authority, status, reputation, and trust.
Finally, there is pathos, which appeals to our emotions. For example, Aristotle argued that, if you want to incite a crowd to anger, what you have to do is say they have been wronged in some way by this thing, or those people, and that they are justified in inflicting harm on that thing.
Of course, the art of persuasion is about navigating all three. How much weight you give to either depend upon the situation you are in, and the person you are speaking to. Aristotle argued that logos is the most important, but we might today disagree with him. So, the next time somebody tries to appeal to your emotions, or sell up their credentials, beware of Aristotle, because they might be trying to persuade you, or even manipulate you in your beliefs.