A testimonial is an endorsement.

These endorsements often come from regular people giving positive reviews of products or ideas. However, the more famous or respected an individual is, the more powerful his or her testimonial will be in the eyes of the public. This is sometimes referred to as an “expert” opinion.

You’ll often see testimonials on websites selling particular products. Here’s a testimonial from a user, DennisB, at Namecheap (a website domain registrar):

“I’ve been using namecheap to register domains for about 3 years. The user interface and delivery times are excellent and I recommend their service.”

You can think of this as a positive review, spotlighted to encourage new customers to sign up for their service.

Expert opinion propaganda, while also involving testimonials, focuses on endorsements by famous or respected individuals. Those using this technique rely on the idea that an audience will follow their favorite celebrities or other respected “experts,” like scientists or academics.

Whenever you see an advertisement with a celebrity on television, you can bet the people behind it are hoping you’ll say, “If they like it, I’ll like it, too!” They want you to both identify yourself with the person and accept their point-of-view.

Examples of testimonial propaganda include:

Testimonial Propaganda: Dentists

“#1 Dentist Recommended Brand”

Wheaties cereal often includes sports figures on the covers of their boxes:

Testimonial Propaganda: Wheaties

Sofia Vergara for CoverGirl:

Testimonial: Sofia Vergara

Shaq endorses a Buick:

And oh, wait, I almost forgot…

Testimonials may also come in the form of political endorsements during a campaign:

When faced with a testimonial or expert opinion propaganda, an individual should follow his or her own judgment and research the item or idea being proposed. Never rely on the word of a single source.

Of course, if the expert or individual is qualified, there is little harm in citing his or her words in an argument. This may effectively support your position. However, words and “opinions” alone should not be an argument’s foundation.