The conclusion. Former Newfoundland premier Joey Smallwood once said about giving speeches: "First I tell them what I'm going to tell them, then I tell them, then I tell them what I told them." That's how you write an essay. In the conclusion, tell them what you told them. Sum up your argument by restating your thesis statement and reminding the reader what your three reasons were. In an argumentative essay, you can finish with a "call to action" -- tell the reader what you would like them to do as a result.