We saw in Chapter 5 that valid arguments are those in which the inference from evidence to claim is properly warranted. Now we will continue our analysis of inferences by examining the nature of fallacies and considering some common types.1

Not only is everyday argumentation cast in language, and therefore inexact, but it takes place in specific contexts. At various points throughout the book, it has been necessary to remark that the application of a principle or guideline depends on context. There are few if any rules that are universally applicable.

In Chapters 4–6, we have considered factors that strengthen or weaken individual arguments, focusing especially on the evidence on which an argument is based and on the patterns of inference that are expressed in various argument schemes. Usually, though, these individual arguments are combined into larger units to advance or defeat a resolution, the main claim in a controversy. The structure of subsidiary claims and evidence to support or oppose a resolution is called a case. If the case supports the resolution, it is called an affirmative case (because it affirms) and if it opposes the resolution, it is referred to as a negative case (because it negates).

In Chapter 2, we examined the structure of simple and complex arguments. But whether the arguments were simple or complex, we treated them in isolation, as if we wanted to show what an argument of one kind or another might look like – as an end in itself. Put another way, we wanted to show how we could express beliefs as different series of related statements.

In this chapter, we will be concerned with the relationship between the evidence and the claim. Together with the truth and quality of the evidence, discussed in Chapter 4, this is the major consideration affecting the strength of an argument. The question is what enables the evidence to count as evidence for the particular claim.

The case represents what its advocate believes are the strongest arguments for the claim (usually an explicit or implicit resolution) that the advocate has undertaken to defend. If the selection and arrangement choices described in Chapter 7 have been made with care, there will be a prima facie case – one that seems persuasive at first glance, before anything is said against it. But a prima facie case will not lead an opponent simply to concede on hearing its first presentation. Rather, the burden of rejoinder discussed in Chapter 3 will come into play. The opponent will try to marshal claims and evidence that will either deny the resolution outright or at least raise sufficient doubt about it that the original advocate will need to strengthen the case beyond its first presentation. The burden of rejoinder will continue to move back and forth between the advocates until one is convinced by the other or, more often, until a neutral third party renders a decision in the dispute.