The purpose of persuasion in writing is to convince, motivate, or move readers toward a certain point of view, or opinion. The act of trying to persuade automatically implies more than one opinion on the subject can be argued.
The idea of an argument often conjures up images of two people yelling and screaming in anger. In writing, however, an argument is very different. An argument is a reasoned opinion supported and explained by evidence. To argue in writing is to advance knowledge and ideas in a positive way. Written arguments often fail when they employ ranting rather than reasoning. While your readers may not always agree with your argument, aim to persuade them to respect and consider your thesis/opinion as a valid one.