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As we have seen, all arguments are made up of assertions or propositions that can be sorted into four categories:

All of the kinds of propositions that emerge when we assert something in an argument have what philosophers call a modality. This means that propositions generally indicate — explicitly or tacitly — the character and scope of what is believed to be their likely truth.

Character has to do with the nature of the claim being made, the extent of an argument’s presumed reach. Both making and evaluating arguments require being clear about whether they are necessary, probable, plausible, or possible. Consider, for example, a claim that it is to the advantage of a college to have a racially diverse student body. Is that necessarily or only probably true? What about an argument that a runner who easily wins a 100-meter race should also be able to win at 200 meters? Is this plausible — or only possible? Indicating the character with which an assertion is advanced is crucial to any argument for or against it. Furthermore, if there is more than one reason for making a claim, and all of those reasons are good, it is still possible that one of those good reasons may be better than the others. If so, the better reason should be stressed.

Indicating the scope of an assertion is equally crucial to how an argument plays out. Scope entails such considerations as whether the proposition is thought to be true always or just sometimes. Further, is the claim being made supposed to apply in all instances or just in some? Assertions are usually clearer, as well as more likely to be true, if they are explicitly quantified and qualified. Suppose, for example, that you are arguing against smoking, and the ground for your claim is this:

Heavy smokers cut short their life span.

In this case, there are three obvious alternative quantifications to choose among: All smokers cut short their life span, most do, or only some do. Until the assertion is quantified in one of these ways, we really don’t know what is being asserted — and so we don’t know what degree and kind of evidence or counterevidence is relevant. Other quantifiers include few, rarely, often, sometimes, perhaps, usually, more or less, regularly, occasionally.

Scope also has to do with the fact that empirical generalizations are typically contingent on various factors. Indicating such contingencies clearly is an important way to protect a generalization against obvious counterexamples. Thus, consider this empirical generalization:

Students do best on final examinations if they study hard for them.

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Are we really to believe that students who cram (“study hard” in that concentrated sense) for an exam will do better than those who do the work diligently throughout the whole course (“study hard” in that broader sense) and therefore do not need to cram for the final? Probably not; what is really meant is that all other things being equal (in Latin, ceteris paribus), concentrated study just before an exam will yield good results. Alluding in this way to the contingencies — the things that might derail the argument — shows that the writer is aware of possible exceptions and is conceding them from the start.

In sum, sensitivity to both character and (especially) scope — paying attention to the role played by quantifiers, qualifiers, and contingencies and making sure you use appropriate ones for each of your assertions — will strengthen your arguments enormously. Not least of the benefits is that you will reduce the peculiar vulnerabilities of an argument that is undermined by exaggeration and other misguided generalizations.