Using the impact of personal experience may not have scientific merit or statistical clout, but it can be very convincing. Reading the autobiography of Olaudah Equiano the story of his capture in Africa, his transport to America and his life as a slave (you can read excerpts of Equiano's account from a collection of slave narratives available on a University of Houston web-site) is an overwhelming experience, convincing us on a personal level much more readily of the evils of slavery than a whole volume of statistics and demographics about the Atlantic slave trade could do. Still, citing personal experience is seldom enough to make a truly compelling and convincing argument. If personal experience is all we have to go on, our argument could be dismissed as being merely anecdotal or idiosyncratic. Personal experience can accompany or reinforce an otherwise sound argument, but it is seldom entirely persuasive in itself.
The other sub-sections of this part of Principles of Composition are as follows: