The Toulmin Schema

Use of the Toulmin schema is not an expression of admiration of Toulmin as a philosopher generally. The schema is good irrespective of the arguments it was designed to support.

Basically the schema comprises the following elements

• Data, a proposition about the world;
• Warrant, a reason for believing that proposition true;
• Backing, a general rule which associates the warrant with the data;
• Claim, a proposition claimed to be consequent on the data;
• Qualifier, a qualification of the claim (e.g. ‘probably’); and finally
• Rebuttal, evidence casting doubt on the claim.

This can be diagrammed:

data -------------> So, qualifier, claim
          |          |
          |          |
        Since       Unless
        warrant     rebuttal
          |
          |
    On account of
       backing

(after Toulmin, S. (2003). The Uses of Argument (2nd ed.). Cambridge: Cambridge University Press. doi:10.1017/CBO9780511840005)

Note that in this, warrant, backing, claim and rebuttal can all be the claims of further Toulmin structures.

For our purposes, a claim shall be a tuple comprising a verb and several optionally qualified nouns; this allows us to do a form of predicate caluculus on claims. The full detail of this implementation requires work.

Toulmin structures are not necessarily – indeed may not be – the most convenient representation for the comprehend stage of the pipeline; but they are likely to be the structures used in search and filter phases and thus delivered back to compose, and so if queries can be represented as partially completed toulmin structures.