Teaching Critical Thinking

Understanding & Evaluating Arguments

Building Blocks of Arguments

In a model developed by Stephen Toulmin, arguments have three basic building blocks—claims, evidence and warrants.

Claims are statements writers or speakers would like audiences (one or more people) to accept as true. Claims may be limited by qualifying statements (e.g., “Honesty is the best policy, most of the time.”) or by explanations of exceptions (e.g., “Honesty is the best policy, except when others’ feelings will be needlessly hurt.”). Often an argument will advance a main claim, which in turn may be supported by subclaims.

Evidence consists of facts, statistics, examples, expert opinions, and previously established claims (including premises already accepted by the audience).

Warrants provide reasoning that justifies the movement from evidence to claims. Sometimes warrants themselves require backing by evidence and reasoning.


Argument Structure

The simplest arguments present only a main claim, which is directly backed with evidence:

“George must be a vegetarian. I’ve never seen him eat meat.”

More complex arguments present a main claim supported by subclaims. For instance, a writer or speaker may simply list several reasons why a claim is true:

“You should consider buying a Funkster guitar. They sound great, they’re very playable, and they’re a good buy for the money.”

Still more complex arguments present a series of related subclaims leading to the main claim:

“The United States government should do more to promote research and investment in technologies that use clean, renewable energy sources. Increased research and investment would bring down the cost of such technologies, then more individuals and companies would use them. This would reduce American dependence on foreign oil and protect the environment, and this in turn would dramatically improve America’s relations with other countries.”

Parts of an argument may be missing, either because they are implied or because the argument is incomplete and therefore flawed. (Of course, arguments that are not incomplete can also be flawed, as the sections on argument structure and reasoning about evidence will discuss.)


Evaluating Arguments

Evaluating an argument requires several skills:

  • Analyzing the purpose of the argument.
  • Recognizing the main claim and evaluating how it is expressed.
  • Understanding and evaluating the structure of the argument.
  • Evaluating the reliability of evidence.
  • Understanding and evaluating reasoning about evidence.