I've always wondered why candidates have to "approve this message"; I mean, if President Obama is on camera talking about himself, then can't I assume he approves the message? Why does he have to state that he approves it at the end?

There's certainly a law that governs what must be said at the end of a political advertisement, or else President Obama wouldn't say exactly the same thing as every other politician at the end of an ad, but there's also an element of persuasion at work here. By appearing on camera saying that he approves the content, the President is giving the ad credibility. It's about him, his work, and his beliefs, and by saying he has approved the ad, President Obama is saying, "You can trust this information about me."

This appeal to credibility is known as "ethos." Ethos is a method of persuasion in which the speaker or writer (the "rhetor") attempts to persuade the audience by demonstrating his own credibility or authority. I think the best way to understand this kind of appeal to the credibility of the author is to look at the three most common ways a rhetor attempts to demonstrate authority on a topic.

By now, you've hopefully gotten an idea of what ethos is: an attempt to persuade by appealing to authority or credibility. You might be wondering, though, what ethos looks like in writing or in speaking. Here are a few examples:

  • References to work experience or life experience related to the topic. When an author writing about the stock market talks about his years working for an investment bank, that's an appeal to credibility.

  • References to college degrees or awards related to the topic. When your biology instructor makes clear in the syllabus that he has a PhD in biology and that you'll be using the textbook he's written for the class, he's reminding you of his authority and credibility on the subject.

  • References to the character of the writer. When a politician writes in a campaign brochure about his years of public service and the contributions he's made to the community, he's letting you know he's trustworthy, a good person, and a credible source of information about the community and the issues that affect it.

  • The use of supporting sources written by authorities on the subject. When a student writes a paper about why school hours should be changed and uses quotations from principals, teachers, and school board members (all of whom know something about the topic), he's borrowing their credibility and authority to increase his own.

  • References to symbols that represent authority. When a candidate gives a speech in front of an American flag, he or she is associating him- or herself with the symbol and borrowing the authority it represents.

See also:

Fallacious Ethos