About 2400 years ago the Greek philosopher Aristotle coined three forms of rhetoric - logos, ethos and pathos - that are prevalent in almost all arguments.
Ethos (Credibility), or ethical appeal, is appeal based on the character of the speaker. One way to do this is to build a case for your authority on the topic.
Pathos (Emotional) is an appeal to the reader’s emotions. One way to do this is to include research that will trigger emotional involvement in your topic.
Logos (Logical) is appeal based on logic or reason. Logos necessitates a well researched and well supported essay that reaches a logical conclusion based on the evidence.