Logos or the appeal to logic, means to convince an audience by use of logic or reason.

To use logos would be to cite facts and statistics, historical and literal analogies, and citing certain authorities on a subject. Logos is the Greek word for “word,” however the true definition goes beyond that, and can be most closely described as “the word or that by which the inward thought is expressed" and, "the inward thought itself" (1). The word “logic” is derived from logos.

Logos can be developed by using advanced, theoretical or abstract language, citing facts (very important), using historical and literal analogies, and by constructing logical arguments.

Logos in Academic Writing

In academic writing, a writer uses logos by supporting his or her thesis with evidence from credible sources and by clearly and logically arranging his or her argument. Evidence can be facts, statistics, historical references, scientific findings, or even literary allusions. All evidence should be true and from credible sources. Sources should also be relevant, properly cited, and in most cases current.

The objective of academic writing is to compel readers to buy into a thesis by making that thesis easy to comprehend and accept. If a paper presents an argument that is confusing or illogical, readers will not find it convincing; therefore, academic writing must flow and avoid logical fallacies. Gaps or leaps in logic will diminish a piece’s logos, as will generalizations or broad statements supported by little evidence. 

Logos in academic writing also depends heavily on audience awareness. Addressing readers’ concerns with logical solutions and directly refuting their counter arguments are effective ways to include logos and convince an audience to accept a thesis. 

Logos in Advertising 

Advertisers use logos to convince people to invest money and/or time into a product, service, event, person, or organization. The purpose of an advertisement is to get people to do something that will ultimately benefit the advertiser, and logos is an important tool advertisers use to reach their target audiences and achieve their marketing goals.

Logos is commonly used in advertisements having to do with nutrition, money, performance, or politics, which can all be shown with numbers. Think calories, financial returns, miles per gallon, employment rates, etc. Numbers and statistics are compelling ways advertisers use logos to convince people to buy what they’re selling.  

Another common way advertisers use logos is by presenting an “if/then” argument. By using convincing images and/or language, many ads lead consumers to believe that if they purchase a product or service, then they will have more fulfilling lives or be more attractive, successful people; if they do what the ad suggests, then they will solve a problem the ad has convinced them they have.  

Take a look at the Popchips ad below for an example of logos in print advertising. 

By presenting nutritional facts and using a logical comparison, Popchips uses logos to show that their chips are better for consumers than their competitors’ chips. The visual aspect of the ad also appeals to the audience’s sense of logic, because who wouldn’t want a bigger stack of chips? This ad uses a common form of logos with a “more bang for your buck” strategy that works well not only in advertisements for food products but also in ads regarding money or performance. Finally, this ad presents the “if/then” strategy by arguing that if you buy Popchips, then you will be a healthier person. 

Logos in Public Speaking and Oral Presentations

Speakers and presenters use logos when they support their assertions with facts, cite credible sources, quote reliable experts, and present clear lines of reasoning. Arrangement is also important. By first establishing ethos, or likability and credibility, a speaker will then be able to effectively use logos. If the audience doesn’t trust the speaker, then the audience won’t likely trust the information presented by the speaker. 

Delivery is another important way speakers use logos. By speaking clearly and in a convincing tone, and by using timing and pauses to reinforce important facts and claims, a speaker can easily appeal to his or her audience. When delivering citations, effective speakers do so as naturally as possible by citing only what’s necessary; they don’t let citations overshadow the facts and interrupt the flow of the argument. 

Take a look at Graham Hill’s TED talk Less Stuff, More Happiness for an example of effective logos in public speaking:

Notice how Hill uses logos by presenting statistics to support his thesis, and he logically arranges his speech by using a convincing “cause and effect” strategy. Because Hill has already established himself as a credible researcher and public speaker, he doesn’t need to cite his sources; he would if he were a student or amateur. 

Hill’s delivery is particularly appealing and positively affects the impact of his logos. He is confident and obviously well-practiced, and he uses a clear tone and an easy-to-follow pace. Notice how he subtly pauses after important facts and assertions, and he consistently reinforces his thesis without being obnoxious or monotonous. 

Hill also uses logos by showing his audience how he personally applied his principles to his own life, which leads the audience to think, “If he can do it, then I can do it.” Hill shows that he understands his audience by presenting examples that are relatable and easy to understand.  At the end, he addresses his audience’s potential counter arguments or concerns and presents practical solutions. Finally, the images throughout the presentation reinforce the facts and make the argument seem logical and attainable.