TOULMIN LOGIC

Credited to historian & philosopher Stephen Toulmin, Toulmin logic is a generally accepted standard for the logical, objective examination of claims made by scientists. Toulmin logic bolsters the Scientific Method and demands that the individual asserting a claim be honest and objective.

4 factors in toulmin logic Claim Data Warrant Backing

You already know that to make an argument, you need at least two things:  a thesis or claim and evidence or data to support the claim. But, as we just discussed, facts (data) don't speak for themselves. Say we have the following datum: Many people who have been hypnotized recall alien abduction scenarios. And we want to use this datum to support the following claim: Alien abduction is a real phenomenon. What else do we need? What’s missing? 

What's missing is what we call the warrant, the connection between data and claim, the thing that speaks for the facts.    In this example, the warrant is: Hypnosis is a valid means of recovering suppressed memories.

CLAIM: Aka “thesis,” “your point,” etc. DATA: Can use any number of different types of evidence; exactly what evidence is accepted depends on rhetorical situation. The WARRANT connects claim and data. an “inferential leap” between these two. performs a "linking" function by establishing a mental connection between the data and the claim

If you present the datum “He really loves kids” to support the claim, “Bill is going to be a really good teacher,” what is your warrant? If you claim that “Debbie is a liar,” and your evidence/data is, “Debbie’s told us ten things about the Johnson Contract and all ten have turned out to be untrue,” the warrant is __________________.

OK, so why is this important? Because a lot of the time, the warrant is     1) not revealed, only assumed; and     2) not necessarily true. To determine whether a warrant is true or not, we examine the evidence for it. Toulmin called this evidence BACKING.

WARRANTS can be very difficult to detect, because they are often based on very common patterns of reasoning or very common values. They can be based on LOGOS evidence, ETHOS evidence (such as an authoritative source, shared values, or sensus communis [“common sense”], or PATHOS evidence. The evidence for the WARRANT is called the BACKING.

But Because They’re Hard to Detect -- -- It’s especially important to find them. Very often, when someone is trying to put a fast one by you, they’re doing it through the warrant. Or when people think sloppily, they’re using an invalid warrant. Very often, the best way to critique an argument is through its warrants.

from Patricia Cornwell’s Portrait of a Killer: Jack the Ripper -- Case Closed Cornwell’s central claim is that Jack the Ripper was really Walter Richard Sickert, a relatively well-known English painter of the late 19th Century.  

Claim: Sickert was Jack the Ripper. DATUM: One of the letters that purported to be from Jack the Ripper was written on the same brand of stationery as a letter from Sickert. WARRANT: ___________________

Claim: Sickert was Jack the Ripper. DATA: Sickert had an operation as a child that left him unable to have a normal sex life.  We know today that many serial killers are impotent. WARRANT: ___________________

Claim: Sickert was Jack the Ripper. DATA: Sickert painted a picture in 1908 called "Jack the Ripper’s Bedroom," described by an art historian as being "very dark and disturbing."  Sickert often painted scenes of violence against women.  WARRANT: ___________________