Introduction to Toulmin Logic Scott Hale English

Logos n What do we mean by “logical structure?” n Chain of Reasoning and Support

Formal Logic vs. The REAL World...

Formal Logic n Operates according to prescribed values and methods n IF q=r n AND r=t n THEN q=t

REAL World n Prescribed rules and methods fail... n IF bad students fail classes n AND John fails a class n THEN John is a bad student?

The Difference? n Formal Logic=universal abstractions n REAL World=specific actualities n Formal Logic=SYLLOGISM n REAL World=ENTHYMEME

SYLLOGISM... n Aristotle called a “complete logical structure” n Three parts: n Specific Premise n General Premise n Conclusion

Example... n Fred is a dog n Dogs are red n Therefore… n Fred is red n Syllogisms provide the specific and general premises and ask the audience to supply the conclusion…

But what happens if…? n You’re given the conclusion and one of the premises… n Socrates is mortal n Socrates is human n What’s missing? n The general premise... n Humans are mortal

ENTHYMEME n Aristotle called an “incomplete logical structure” n The enthymeme consists of a claim (conclusion) and a reason (suggests the specific premise) n All enthymemes then hinge upon an unstated assumption (general premise)

Example… n Fred is red because he is a dog… n Claim/Conclusion=Fred is a red n Reason/Suggests Specific premise=Fred is a dog n Assumption/General premise=Dogs are Red

Toulmin Logic n A method for the construction and analysis of arguments n Builds upon the enthymeme by supplying the unstated assumption/general premise n Calls the assumption into question by requiring support for it

Toulmin Terms: n Claim (conclusion) n Reason (support/explanation for conclusion) n Grounds (specific premise) n Evidence (support for Grounds) n Warrant (unstated assumption/general premise) n Backing (support for warrant)

Developing the Toulmin schema n Develop enthymeme (Claim and Reason) n To develop Grounds: Link Subject of Claim to Predicate of Reason n To develop Warrant: Link Category of Predicate of Reason to Predicate of Claim

Example... n Enthymerme: Fred is red because he is a dog n Claim: Fred is red n Reason: because he is a dog n Grounds: Fred is a dog (specific premise) n Warrant: Dogs are red (general premise)

Evidence and Backing n Evidence supports the Grounds (specific premise) and will always directly refer to the subject n Backing supports the Warrant (general premise) and will never refer directly to the subject, but instead to the category of the subject

Example… n C: Fred is red n R: b/c he is a dog n G: Fred is a dog n Evidence: Support that Fred is a dog-- expert testimony, data, etc n W: Dogs are red n B: Support that Dogs are red--expert testimony, data, other examples

Qualifiers n A qualifier limits the force of a claim by pointing to any exceptions to a rule and indicating how the condition would have to change in order for the understanding (epistemology) to change

Examples… n Some dogs are red n Only when he is sunburned is Fred red n Unless it is Friday, I am going to study tonight