Logic deals with the analysis and evaluation of arguments. Since arguments are expressed in language, the study of arguments requires that we should pay carefully attention to language in which arguments are expressed. If you reflect on how language is used are everyday life, you can notice that our ordinary language has different uses.
Language has a variety of functions. By using language we do various things like stating facts, reporting events giving orders, singing songs, praying God, making requests, cutting jokes, asking questions, making promises, greeting friends and so on. These are wide varieties of language uses. We will not make any attempt to provide an exhaustive list of language uses. Rather we shall discuss here a broad classification of some of the important uses of language. There are three important uses of language that we shall discuss here. These are: (a) Descriptive, (b) Emotive, and (c) Directive uses of language.
(a) Descriptive Use of Language:
Language is often used to describe something or to give information about something. So the descriptive use of language is also called informative use of language. When a sentence is used descriptively it reports that something has some feature or that something lacks some feature. Consider the following two sentences:
1. Birds have feather.
2. Birds are not mammals.
The first sentence reports that having feather is a feature of birds. The second sentence reports that birds do not have some essential qualities found in mammals. In, either case it provides information about the world. Both affirmation and denial about things in the world are examples of descriptive use of language. The following are some more examples of language functioning descriptively.
1. Crows are black.
2. Mumbai is not the capital of India
3. A spider has eight legs.
4. Logic is the study of correct reasoning.
5. The 15th of August is Indian Independence Day.
All these above statements happen to be true statements. However, it should be noted that only true sentences are instances of informative use of language, but also false sentences are instances of informative use of language. "A spider has six legs" is a false statement since spiders in fact have eight legs. Yet the statement "A spider has six legs", even though false, is nonetheless an example of descriptive use of language.
When language functions informatively we can sensibly ask whether what is asserted is or false. In other words, the question "Is it true?" can be meaningfully asked of all such instances. When language is used to affirm or deny any proposition, its function is informative; Language used to present arguments serves informative function.
All descriptions of things, events, and their properties and relations consist of informative discourse. The language of science is a clear instance of descriptive use of language.
(b) Emotive Use of Language:
Language is often used to express our feelings, emotions or attitudes. It is used either to express one's own feelings, emotions or attitudes, or evoke certain feelings, emotions or attitudes someone else, or both.
When one expresses feelings while alone, one is not expressing it to evoke feelings in others. But very often we attempt to move others by our expressions of emotions, in all such cases language is used emotively. Consider the following utterances:
1. Jai Hind!
3. it’s disgusting!
4. it’s too bad!
5. it’s wonderful!
6. Let's win this game!
In appropriate contexts all these can count as instances of language functioning emotively.
If a sentence is followed by an exclamation mark, then very likely it is used emotively. The language of poetry also provides an example of language serving the expressive function Emotive use is different from descriptive use of language.
Emotive or expressive discourse is neither true nor false. When language is used emotively, it cannot be characterized as true or false. We can, however, respond to it by asking questions such as "Is the person sincere?" and "How should I feel?" Expressive use of language is also different from directive use of language
(c) Directive Use of Language:
Language is often used to give direction to do or not to do something. Commands, requests, instructions, questions are instances of directive use of language. Consider the following examples:
1. Finish your homework.
2. Wash your clothes.
3. You should wear helmet when riding a scooter.
4. Don't smoke.
5. Are you feeling well?
6. Will you please help me?
In all these above examples language is functioning directively. Anyone who utters any of these sentences, in a typical situation, is directing someone to do something or to respond in an appropriate manner.
In all instances of language functioning directively, we can meaningfully ask the question "Should I respond?" You will notice that directive, discourse, like emotive discourse, is neither true nor false. But directive discourse, specially the imperative statements, can figure in some arguments.
A command such as "Close the window", or an advice such as "You should wear helmet while riding scooter" is either obeyed or disobeyed, but it is neither true nor false. Through commands, advices, and requests are neither true nor false, these can be reasonable or unreasonable, proper or improper. These characterizations of imperative statements are somewhat analogous to characterisation of informative statements as true or false.
Moreover, imperative arguments often imply or presuppose the truth of some propositions. If I request you to close the window, my request presupposes the truth of the proposition that the window is open.
Since reasons can be cited for or against imperative statements, such statements do occur in imperative arguments. We are not going to discuss the logic of imperatives in this book. In our study of logic we shall restrict our discussion to arguments that are stated in the language that functions informatively.
The study of logic is concerned with language that functions informatively. So it is important distinguish language that is informative from language that serves other functions.
There is, however, no mechanical method for distinguishing informative use of language from language that serves other functions. Grammatical structure of a sentence often provides a clue to its function, mere is no necessary connection between function and grammatical form. We can determine whether the language in a particular context is functioning informatively or not by asking "Is this instance of language being used to make an assertion that is either true or false?" If the answer is yes'' then it is an instance of informative use of language.
It should be noted that language, in particular contexts, very often functions in more than way. One and the same sentence might have more than one function. For effective communication language is often used deliberately to serve multiple functions.
Language used to the expressive function might contain some relevant information. So also language that is primarily informative may make use of other functions as well. Most discourses in our ordinary communication contain elements from all the three uses of language enumerated above. In logic restrict our attention to those cases where our discourse is at least partly informative or descriptive.