64 Three Forms of Proof

The psychologist Carl Hovland and his associates did conducted well-regarded social science research in the 1950s and 1960s to rediscover what Aristotle had noted 2500 years before in his book titled On Rhetoric . In his words, “Of the [modes of persuasion] provided through speech there are three species: for some are in the character of the speaker, and some are in disposing the listener in some way, and some in the argument itself, by showing or seeming to show something ” (Aristotle 1356b). We know the three species as:

  • The logic of the argument (logos)
  • The credibility of the speaker (ethos)
  • The emotions of the audience (pathos)


Logos is the use of logic to persuade your audience. A logical argument usually convinces its audience because of the perceived merit and reasonableness of the claims and proof offered in support of the overall thesis, rather than because of the emotions it produces in the audience (pathos) or because of the status or credentials of the speaker (ethos). We often spend most of our time in speech development thinking about the logical elements, but we should remember that logic is only one leg of the three-legged stool of persuasion.


If any one form of proof can be seen as most important, it would be speaker credibility. There are three characteristics that may or may not add to a speaker’s credibility. These characteristics are good sense, good will, and good moral character. We tend to believe those people we think are smart or have good sense. This is especially true if the person is deemed to have good sense in general but more so if s/he is seen as being knowledgeable about the topic at hand. This is why you want to let the audience know that you are informed on the topic of your talk, that you have personal experience, or that you have done your research.

The next aspect of credibility deals with your goodwill. This refers to how the audience members judge the speaker’s intentions. Think about buying a car. Sadly, most people do not trust car salespeople. A car salesperson is seen as being out for herself/himself and not having our best interests at heart when s/he says, “This is a great car, and I can let you have it for a really good price. ” We do, however, believe our dentist when s/he says, “This tooth has to come out. ” We see our dentist as having our best interests at heart, even though we know s/he will make money removing the tooth, just as a salesperson earns a commission by making a sale.

The last aspect of credibility is the speaker’s image, the perception that the speaker has good moral character or is an honest person. Let others know that you cheat on your taxes, speed in your car, or plagiarize papers, and they are less likely to believe you on other topics.


Pathos is used to describe the speaker’s attempt to appeal to an audience’s sense of identity, their self-interest, and their emotions. If the speaker can create a common sense of identity with her/his audience, then the speaker is using a pathetic appeal, or a rhetorical appeal using pathos. Pathos most often refers to an attempt to engage an audience’s emotions. Think about the different emotions people are capable of feeling: love, pity, sorrow, affection, anger, fear, greed, lust, hatred, and so forth.

Let’s say you are trying to convince an audience to donate money to a hurricane relief fund. The rhetoric can make pathetic appeals to an audience’s feelings of love, pity, and fear. The extent to which any of these emotions will be successfully engaged will vary from audience to audience. Love will be invoked if the audience can be made to feel their fundamental connection to other human beings. Pity will be felt if the plight of the homeless hurricane victim can be made vivid to the audience. Fear might work if the audience can be made to imagine how they would feel in a hurricane victim’s place. If the speaker uses these appeals properly (and also properly uses ethos and logos), then the audience is more likely to be persuaded.


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