Stephen Edelston Toulmin (born March 25, 1922) is a British philosopher, author, and educator. Influenced by the Austrian philosopher Ludwig Wittgenstein, Toulmin devoted his works to the analysis of moral reasoning. Throughout his writings, he seeks to develop practical arguments which can be used effectively in evaluating the ethics behind moral issues. The Toulmin Model of Argumentation, a diagram containing six interrelated components used for analyzing arguments, was considered his most influential work, particularly in the field of rhetoric and communication, and in computer science.

Stephen Toulmin is a British philosopher and educator who devoted to analyzing moral reasoning. Throughout his writings, he seeks to develop practical arguments which can be used effectively in evaluating the ethics behind moral issues. His most famous work was his Model of Argumentation (sometimes called “Toulmin’s Schema,” which is a method of analyzing an argument by breaking it down into six parts. Once an argument is broken down and examined, weaknesses in the argument can be found and addressed.

Toulmin’s Schema:

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 1 can support his claim with the supporting data “I was born in Bermuda.”
3. Warrant: the statement authorizing the movement from the data to the claim. In order to move from the data established in 2, “I was born in Bermuda,” to the claim in 1, “I am a British citizen,” the person must supply a warrant to bridge the gap between 1 & 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.”
7. The first three elements “claim,” “data,” and “warrant” are considered as the essential components of practical arguments, while the 4-6 “Qualifier,” “Backing,” and “Rebuttal” may not be needed in some arguments. When first proposed, this layout of argumentation is based on legal arguments and intended to be used to analyze arguments typically found in the courtroom; in fact, Toulmin did not realize that this layout would be applicable to the field of rhetoric and communication until later.

Here are a few more examples of Toulmin’s Schema:

Suppose you see a one of those commercials 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 attract guys.”
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.

Another example:

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.

Another example:

1. Claim: Flag burning should be unconstitutional in most cases.
2. Data: A national poll says that 60% of Americans want flag burning 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”

Toulmin says that the weakest part of any argument is its weakest warrant. Remember that the warrant is the link between the data and the claim. If the warrant isn’t valid, the argument collapses.