The Toulmin method is an informal method of reasoning. Created by the British philosopher Stephen Toulmin, it involves the grounds (data), claim, and warrant of an argument. The Toulmin method suggests that these three parts are all necessary to support a good argument. The grounds are the evidence used to prove a claim. The warrant is the assumption or principle that connects the grounds to the claim. All three parts are critical to achieving rhetorical analysis.
For an example: "Harry was born in Bermuda, so Harry must be a British subject."
In the above sentence, the phrase "Harry was born in Bermuda" is the data. This is evidence to support the claim. The claim in the sentence above is "Harry must be a British subject." The warrant is not explicitly stated in this sentence; it is implied. The warrant is something like this, "A man born in Bermuda will be a British subject." It is not necessary to state the warrant in a sentence. Usually, one explains the warrant in following sentences. Other times, like in the sentence above, the speaker of the sentence assumes the listener already knows the fact that all people born in Bermuda are British subjects.
Another example: "Steve bought apple juice for himself, so he must like apple juice."
This argument provides the data, claim, and warrant. The data would be the fact that Steve bought apple juice for himself. The claim is that Steve must like apple juice. The warrant is that people who buy apple juice, drink it, which means that they must like it, or else they wouldn't drink it. Again, the warrant is considered background knowledge and unnecessary to repeat in the argument. If one were to expound this argument, however, it would be helpful to explain the warrant.
An author usually will not bother to explain the warrant because it is too obvious. It is usually an assumption or a generalization. However, the author must make sure the warrant is clear because the reader must understand the author's assumptions and why the author assumes these opinions. An example of an argument with an unclear warrant is like this: "Drug abuse is a serious problem in the United States. Therefore, the United States must help destroy drug production in Latin America." This may leave the reader confused. By inserting the warrant in between the data and the claim, though, would make the argument clearer. Something like, "As long as drugs are manufactured in Latin America, they will be smuggled into the United States, and drug abuse will continue." This phrase makes clear why the evidence relates to the claim. One must be cautious as to deciding whether or not to include the warrant in the argument because flaws in the argument could be obvious.
Backing, rebuttals, and qualifiers are also typical additions to this argument. The backing is added logic or reasoning that may be needed to convince the audience and further support the warrant if it is not initially accepted. Rebuttals are used as a preemptive method against any counter-arguments. These acknowledge the limits of the claim, considering certain conditions where it would not hold true. Usually following is a counter-argument or presentation of new evidence to further support the original claim. Qualifiers are words that quantify the argument. They include words such as 'most', 'usually', 'always', 'never', 'absolutely' or 'sometimes'. These can either strongly assert arguments or make them vague and uncertain.
One criticism of the Toulmin method is that it does not consider the question in argumentation. The Toulmin method assumes that an argument starts with a fact or claim and ends with a conclusion, but ignores an argument's underlying questions. In the example "Harry was born in Bermuda, so Harry must be a British subject", the question "Is Harry a British subject?" is ignored, which also neglects to analyze why particular questions are asked and others are not.
- O'connor, D. J. "The Uses of Argument. By Stephen Edelston Toulmin. (Cambridge University Press, 1958. Pp. viii + 264. Price 22s. 6d.)". Philosophy. 34 (130): 244–245. doi:10.1017/s0031819100037220. ISSN 0031-8191.
- "Reasoning". The Bedford Reader. By X.J. Kennedy, Dorothy M. Kennedy, and Jane E. Aaron. Ed. Denise B. Wydra and Karen S. Henry. 9th ed. New York: Bedford/St. Martin's, 2006. p. 519–522.
- Erduran, Sibal (2008). Argumentation in Science Education. Dordrecht: Springer. ISBN 978-1-4020-6669-6.