Another Rhetorical Device would-be Purpose. The purpose is defined as someone who wants to find a reason to make sure that their task is done or dealt with. Also, a purpose shows how argumentative one could be because they would want to make sure that everyone in their path understands where their coming from. A purpose can benefit a lot of people, only if it is completely understandable and not sane. It is to show one’s intentions or objectives based on their argument.