2.1: Arguments

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Inferences and Arguments

We draw an inference when we make a judgment based on some evidence, assumptions, or reasons. For instance, you learn that 87% of the people in a carefully conducted poll plan to vote for the Republican candidate for Congress. So, you infer (or conclude) that the Republican will win. The results of the poll provide a reason to draw this conclusion. Inference is an activity or process, something we do when we draw a conclusion from assumptions or premises.

By contrast, arguments (as we will use the term) are not processes but groups of sentences. Still, we can often study and evaluate inferences by looking at the argument patterns they involve. You learn that 87% of voters plan to vote Republican and conclude that the Republican candidate will win. This inference or reasoning follows the contours of an argument. Our reasons are the premises of the argument, and the new belief is the conclusion. Thus, our inference about the election involves the following argument:

Premise: 80% of people surveyed plan to vote Republican.

Conclusion: The Republican congressional candidate will win.

In a good argument, the premises justify or support the conclusion; they provide good evidence for it.

An argument consists of two things:

A group of one or more sentences – the premises
One further sentence – the conclusion

Any time someone gives reasons to support a claim, they are giving an argument. Their argument makes a claim; this claim is its conclusion. The premises are intended to provide reasons (justification, support, evidence) for the conclusion. Some arguments are good and some aren’t. In a good argument, the premises really do provide a good reason to think that the conclusion is true. Sometimes we also call premises reasons, or assumptions.

The sentences that make up an argument must all be ones that can be either true or false. So, an argument consists of declarative (or indicative) sentences (rather than commands or questions). In everyday life, we often think of an argument as a dispute or disagreement in which people shout at each other. But for purposes of critical reasoning, an argument is just a group of declarative sentences: one of them is the conclusion; the rest are premises.