"We believe good men more fully and more readily than others," at least that's how Aristotle defined ethos.
Ethos is just one point on the rhetorical triangle and has to do with how people perceive you. As an author, are you competent, fair, and/or an authority on your subject matter? If you want people to believe your premise, or message, you better be.
An August 2011 article in the Chronicle of Higher Education asserts that "ethos is the primary mode of persuasion, and one which we neglect at our peril. Reflect for a moment on how you have been persuaded. When you were a student, which teacher influenced you the most? Probably the one whose character and interaction with students you found most appealing. Which publications do you trust the most? Probably the ones with the best brand (branding being our impoverished substitute for ethos)."
Branding? Yes, branding, as in advertising. And advertisers are experts at manipulating people using ethos, pathos, and logos. They are trying to get you to do something--whether it is believing in a message (think politics) or buying products--you are being manipulated.
So think about ethos or ethical appeals using trustworthiness, credibility, expert testimony, and reliability as you watch these two McDonald's commercials:
Why do you think McDonald's remade this commercial using LeBron James and Dwight Howard?
But it isn't just athletes that give ethos to McDonald's, especially in Japan.
In both sets of McDonald's commercials, the hamburger chain uses ethos in very different ways. How is McDonald's using ethos in each case?
If you were an advertising executive, who would you perceive to be your target market and where would you position these sets of ads?