Our study of logic will be limited to deductive logic; and, even within those bounds, we will consider only the logical forms that are part of first-order logic. These limits imply some others that deserve consideration in their own right: although our study of deductive logic can be seen as the study of meaning, we will not study all aspects of meaning.
1.3.1. Three complications
The simple picture of language outlined in section 1.2.4 is too simple in many respects, but three are especially important for our purposes. One is that sentences are not used only to convey information.
1.3.2. Indexicality and vagueness
Even when a sentence conveys information, the information that is conveyed will usually depend on the context in which the sentence is used.
1.3.3. Implication and implicature
Communication often exploits the assumption that what a speaker says is not only true but satisfies certain other requirements.
1.3.4. Presupposition
Another way of conveying information rests on the possibility of sentences not having truth values at all.