The formal patterns of correct reasoning can all be conveyed through ordinary language, but then so can a lot of other things. In fact, we use language in many different ways, some of which are irrelevant to any attempt to provide reasons for what we believe. It is helpful to identify at least three distinct uses of language:
1. The informative use of language involves an effort to communicate some content. When you tell a child, “The fifth of May is a Mexican holiday,” or you write that “Logic is the study of correct reasoning,” or you jot a note to yourself, “Jennifer—555-3769,” you are using language informatively. This kind of use presumes that the content of what is being communicated is actually true, so it will be the central focus in the study of logic.
2. An expressive use of language, on the other hand, intends only to vent some feeling, or perhaps to evoke some feeling from other people. When you say, “Friday afternoons are dreary,” or yell “Ouch!” you am using language expressively. Although such uses don’t convey much information, they do serve an important function in everyday life, since how we feel sometimes matters as much as (or more than) what we hold to be true.
3. Finally, directive uses of language aim to cause or to prevent some overt action by a human agent. When you say “Shut the door,” or you write “Read the textbook,” or memo to yourself, “Don’t rely so heavily on the passive voice,” you am using language directively. The point in each of these cases is to make someone perform a particular action. This is a significant linguistic function, too, but like the expressive use, it doesn’t always relate logically to the truth of our beliefs.
Notice that the intended use in a particular instance often depends more on the specific context and tone of voice than it does on the grammatical form or vocabulary of what is said. The simple declarative sentence, “I’m hungry,” for example, could be used to report on a physiological condition, or to express a feeling, or implicitly to request that someone feed you. In fact, uses of two or more varieties may be mixed together in a single utterance; “Stop that,” for example, usually involves both expressive and directive functions jointly. In many cases, however, it is possible to identify a single use of language, that is probably intended to be the primary function of a particular linguistic unit.
British philosopher J. L. Austin developed a similar, though much more detailed and sophisticated, nomenclature for the variety of actions we commonly perform in employing ordinary language. While the specifics may vary, some portion of the point remains the same: since we do in fact employ language for many distinct purposes, we can minimize confusion by keeping in mind what we’re up to on any particular occasion.