Using Toulmin Logic
in the Classroom
By Todd Harper
"Be logical," we say to our students, expecting them to show logical reasoning in writing. Yet, many of our students lack a basic understanding of logical argument and its components to effectively persuade others or to critically analyze the arguments they hear. Thus, one important element in the teaching of critical writing and critical thinking skills is to educate students on how arguments are constructed. Below are five terms used by British philosopher and rhetorician Stephen Toulmin to analyze contemporary arguments. Toulmin argues that every effective argument consists of a claim, evidence, explicit and implicit assumptions, qualifiers, and rebuttals. In teaching these terms to students to use in their reading as well as writing, we help them to make clearer and sounder statements.
Toulmin notes that every argument has a claim or thesis, which asserts the author's position on a particular topic. A recent example might be President Clinton's claim that the United States should send troops to the U.N. peace-keeping force in Bosnia. The necessity for U.S. involvement in Bosnia is Clinton's assertion for the position the U.S. should take in this foreign crisis. To support his position, Clinton uses evidence to back up his claim. Evidence can range from empirical data, examples, and anecdotes to more formal modes of inductive and deductive logic. Clinton's claim is grounded in the deductive argument that since the U.S. significantly helped broker the peace settlement, then it should also be involved in securing the peace.
For an argument to be successful, the evidence must support the claim or conclusion. When we ask why a particular set of evidence supports a particular claim, we begin to inquire into the explicit and implicit assumptions of the argument. The explicit and implicit assumptions of an argument are the principles which link evidence to the claims. The assumption for Clinton's argument is that when the U.S. helps to broker peace deals, then it must help see the process through. The backing of an argument entails the institutional and historical support needed to reinforce the implicit and explicit assumptions of the argument. The backing for Clinton's claim has been the historical role the U.S. has played in the U.N. and the U.N. peace keeping negotiations, in particular. Yet, Clinton has also called on the backing of military, congressional, and historical documents as well as contemporary scholarly research within history and political science departments.
The final two elements of Toulmin's structure are qualifiers and rebuttals. The qualifiers limit and qualify the assertion and propositions of the argument. As stated, the qualifiers of Clinton's argument seem absolute in that he does not qualify any of his statements with expressions such as most, some, or few. If he had qualified his argument, Clinton might have said, "If the situation gets worse, we'll send troops to Bosnia." Yet, his absolute provides many in Congress and the military with one of many rebuttals, or statement in opposition to the claim. Several members of Congress have noted that because the government has been involved in peace negotiation, it does not necessarily follow that the U.S. should commit troops. Others have rebutted Clinton's argument with qualifiers to his claim, stating the U.S. only involves its military in peace-keeping forces when there is an adequate American interest in the country.
While Toulmin's terms do not help students
identify whether an argument is "right" or "wrong," they do help students
begin to explore whether or not an argument is logically sound. In the
example of the Clinton argument, students would be able to begin to parse
out the different components to Clinton's assertion. Furthermore, they
would be able to see where further research might be needed in order to
completely determine the strength for Clinton's claim, for example the
historical precedence for military involvement or noninvolvement in other
peace-keeping missions, the reliability of those used to support Clinton's
assertion, etc. . . . Toulmin's method, while not a cure all, does help
students critically analyze an argument by providing concepts to break
the argument into understandable parts.
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