toulmins model of argumentation

Introduction

Stephen Toulmin, an English philosopher, developed a practical approach to analyzing the logic of everyday arguments. His approach involves identifying and separating the various components of an argument into a specific order so that they may be appraised. The model and specific vocabulary that Toulmin employs will be elaborated as required.

Claims

In its most simple form an argument consists of a claim (C), which is the conclusion to be established by the argument. We have already seen that arguments consisting of only a claim or conclusion are Level 1 arguments. Examples would include:

· Vitamins are good for you.
· Breast self-examination saves lives.
· Mrs. Smith should take hydrochlorothiazide.

These claims, on their own, lack any reasoned support to determine whether they are true or false despite the fact that they may be true or false. More is required to establish this.

Data

As arguments are intended to persuade you on the truth or probability of some matter, there is some unresolved issue or decision on which the provision of information depends. When attempting to demonstrate the truth or probability of an argument's claim, one may be asked: "What information have you got to go on?"

The first step to establishing a claim is to have some information that justifies it. Claims are usually supported by appeal to some facts or other considerations. Broadly considered these can be called data (D). Data can be a direct observation, appeal to published literature or any other form of positive or negative information.

During your discussions with Mrs. Smith she may question why she should take hydrochlorothiazide. The response to her question is that she suffers from hypertension.

Warrants

Even after presenting data that acts as the foundation for an argument, you may be asked "How did you get there?". In other words, can you somehow justify the leap from the data you've provided to the claim?

Supporting the step between data and the claim is the warrant (W). A warrant is distinct from the data and the claim and acts as a bridge between them. The movement from data to the claim though the use of a warrant forms a Stage 2 argument. You should note that warrants are often implicit (i.e. left unstated) in arguments.

Mrs. Smith may then ask why this particular medication. Essentially, you are being requested to supply a warrant for your decision. Quite simply, you've prescribed this medication because it is effective at lowering blood pressure.

Backing Up a Warrant

One may call into question the validity of the warrant. To demonstrate the validity of the warrant it may be necessary to introduce additional data, information or possibly other arguments as backing (B) to a warrant.

You've told Mrs. Smith that hydrochlorothiazide will lower her blood pressure. But she may respond "How do you know?".

The range of possible answers available to you as her physician include the following:

1. Because I'm a doctor (intuition/authority)
2. Because in my experience it works (experience)
3. Because it interferes with a specific biochemical process that will lower blood pressure (basic science)
4. Because many well designed studies have shown that the drug is effective in lowering blood pressure (clinical science)

Clearly there is a wide variety of available warrants for use in an argument with some being stronger than others. With the use of stronger warrants we become more confident in the validity of the argument and are more likely to accept the claim.

Qualifiers

As most arguments are not absolute in nature, Toulmin introduced qualifiers (Q) into his model as a way to express the relative strengths of warrants in supporting the conclusions that they justify. If a warrant allows us to unequivocally accept a claim given the appropriate data, we can qualify the claim with "definitely" or "necessarily". If there is any uncertainty surrounding the warrant we may be forced to qualify the claim with terms such as "probably" or "possibly". By convention the qualifier is considered separate from the warrant.

Taking hydrochlorothiazide does not necessarily guarantee that blood pressure will be lowered. In this case we need to qualify our warrant by stating that hydrochlorothiazide is usually effective in lowering blood pressure.

Rebuttals

A rebuttal (R) acknowledges limitations of the argument and may be put forward to indicate conditions in which the warrant is not applicable and consequently the conclusion can be overturned.

A rebuttal in the case of Mrs. Smith may be that she is currently on a medication that interacts with hydrochlorothiazide. A more efficacious medication may be suggested and thus act as a rebuttal. Perhaps Mrs. Smith's particular set of values, whatever they may be, prevent her from using the medication.

With the introduction of qualifiers and the search for counterclaims and rebuttals, the Toulmin model can be used to analyze more complex Stage 3 and 4 arguments such as those commonly encountered in the practice of medicine.