Persuasive Strategies Using Logos

Learning Objectives

Define persuasive strategies using logos.

Recall that logos refers to the use of logical reasoning in an argument.

Using ideas of philosopher Stephen Toulmin, who studied how arguments work in everyday communication, we can break up an argument into different parts to help understand how they are structured

There are six elements for analyzing or presenting arguments that are important to the Toulmin method. When you’re preparing a speech, you can include these elements to ensure your audience will see the validity of your claims.[1]

These are the six parts of an argument in Toulmin’s model:

  1. Claim: conclusions whose merit must be established. For example, if a person tries to convince a listener that he is a British citizen, the claim would be “I am a British citizen.”
  2. Data: the facts appealed to as a foundation for the claim. For example, the person introduced in Part 1 can support his claim with the supporting data “I was born in Bermuda.” The data is your evidence or proof supporting the claim.
  3. Warrant: the reasoning that connects the data to the claim. In order to move from the data established in Part 2, “I was born in Bermuda,” to the claim in Part 1, “I am a British citizen,” the person must supply a warrant to bridge the gap between Parts 1 and 2 with the statement, “A man born in Bermuda will legally be a British citizen.” Toulmin stated that an argument is only as strong as its weakest warrant and if a warrant isn’t valid, then the whole argument collapses. Therefore, it is important to have strong, valid warrants.
  4. Backing: facts that give credibility to the statement expressed in the warrant; backing must be introduced when the warrant itself is not convincing enough to the readers or the listeners. For example, if the listener does not deem the warrant as credible, the speaker would supply legal documents as backing statement to show that it is true that “A man born in Bermuda will legally be a British citizen.”
  5. Rebuttal: statements recognizing the restrictions to which the claim may legitimately be applied. The rebuttal is exemplified as follows: “A man born in Bermuda will legally be a British citizen, unless he has betrayed Britain and become a spy of another country.”
  6. Qualifier: words or phrases expressing how certain the author/speaker is concerning the claim. Such words or phrases include possible, probably, impossible, certainly, presumably, as far as the evidence goes, or necessarily. The claim “I am definitely a British citizen” has a greater degree of force than the claim “I am a British citizen, presumably.”

The first three elements (claim, data, and warrant) are considered as the essential components of practical arguments, while the final three elements (backing, rebuttal, and qualifier) may not be needed in all arguments.

Flow Chart. Fact: Rick has fair skin, red hair and freckles, and he sunbathed all day yesterday. A blue line moves right, and drops down to two pieces. First, Warrant: People with fair skin, red hair and freckles usually get sunburnt easily. Second, Backing: Those people have little melanin in their skin. Melanin protects against sunburn. Continuing on the blue line to the right, we see another two sections. First, (probably) Conclusion: Rick will probably get seriously sunburnt. Second, Rebuttal: Rick's parents both have fair skin, red hair and freckles, and they never seem to get sunburnt however much they sit outside.

Toulmin’s model of argumentation

A Deeper Dive

The following video introduces the components of the Toulmin model.

You can view the transcript for “The Toulmin Model of Argumentation” here (opens in new window).

To Watch: President Obama, “Address to the Nation on Syria”

In this video, Steven Klien, associate teaching professor of communication at the University of Missouri, uses the Toulmin model to analyze President Obama’s 2013 speech announcing air strikes against Syrian government forces. Klien’s explanation of Toulmin’s model is very clear and thorough, so you may want to watch it in its entirety, but for our purposes, the relevant section is 11:47 through 21:00.

You can view the transcript for “The Toulmin Model of Argument” here (opens in new window).


Toulmin’s Method Examples

Example 1

Suppose you watch a commercial for a product that promises to give you whiter teeth. Here are the basic parts of the argument behind the commercial:

  1. Claim: You should buy our tooth-whitening product.
  2. Data: Studies show that teeth are 50% whiter after using the product for a specified time.
  3. Warrant: People want whiter teeth.
  4. Backing: Celebrities want whiter teeth.
  5. Rebuttal: Commercial says, “unless you don’t want to show your real smile.”
  6. Qualifier: Fine print says, “product must be used six weeks for results.”

Notice that those commercials don’t usually bother trying to convince you that you want whiter teeth; instead, they assume that you have bought into the value our culture places on whiter teeth. When an assumption—a warrant in Toulmin’s terms—is unstated, it’s called an implicit warrant. Sometimes, however, the warrant may need to be stated because it is a powerful part of the argument. When the warrant is stated, it’s called an explicit warrant.

Example 2

  1. Claim: People should probably own a gun.
  2. Data: Studies show that people who own a gun are less likely to be mugged.
  3. Warrant: People want to be safe.
  4. Backing: May not be necessary. In this case, it is common sense that people want to be safe.
  5. Rebuttal: Not everyone should own a gun. Children and those will mental disorders/problems should not own a gun.
  6. Qualifier: The word “probably” in the claim.

How would you assess the strength of the warrant in this argument?

Example 3

  1. Claim: Flag burning should be unconstitutional in most cases.
  2. Data: A national poll says that 60% of Americans want flag burning to be unconstitutional.
  3. Warrant: People want to respect the flag.
  4. Backing: Official government procedures for the disposal of flags.
  5. Rebuttal: Not everyone in the U.S. respects the flag.
  6. Qualifier: The phrase “in most cases.”

How would you assess the strength of the data in this argument?

Try It

  1. Toulmin, Stephen. The Uses of Argument. Cambridge University Press, 1958.