The art of persuasion (rhetoric) has three elements: emotion (pathos), deference (ethos), and logic (logos). Imagine this attempt to persuade you to get a dog:
President Obama conducted extensive research and concluded that Portuguese Water Dog is the best choice for families of young children. When Sasha and Malia play with the puppy, no one can stop smiling.
Here we enlisted a respectful figure, presented data, and painted you a heart-warming picture. Studies showed that people are persuaded by emotions, deference, and data — all three, in that sequence. Over-using logos: data, statistics, facts, or logic, sometime to the point of ignoring the other two elements is a common mistake.
Modern knowledge workers, you engineers, designers, architects, and, yes, managers are frequently in the business of persuasion. You need to motivate your staff, make alliance with peers, and align your boss (it works both ways). Your career does not move without persuasive skill in your toolbox.
I interpreted ethos as deference, not authority. Deference comes from respect or trust. It is a powerful persuastive tool, sometime enough by itself. It, however, is completely associated with the individual and takes long time to cumulate.
It is dangerous to persuade by authority. Positional power is addictive, since it is effective, fast, and easy. But many argued it is not really persuation if commanded. Modern knolwedge workers must understand, agree, and communicate with others for the organization to succeed. Authority, best displayed but not used, usually does not work. It is also one tool easiest to lose.
Pathos need not be Hallmark-style dramas. Just stay connected to your audience. Find points that they care. Have eye contact when you deliver the message. Smile and show that you are a human being, not a voicebox that happens to be carbon-based.
This is persuation 101, the basics. Those who have finished this class may proceed to Robert Cialdini.