Implicature

In pragmatics (linguistics), implicature is the relationship between two statements where the truth of one suggests the truth of the other, but—distinguishing implicature from entailment—does not require it. For example, the sentence "Mary had a baby and got married" strongly suggests that Mary had the baby before the wedding, but the sentence would still be strictly true if Mary had her baby after she got married. Further, if we add the qualification "— not necessarily in that order" to the original sentence, then the implicature is cancelled even though the meaning of the original sentence is not altered.

This can be contrasted with cases of entailment. For example, the statement "The president was assassinated" not only suggests that "The president is dead" is true, but requires that it be true. The first sentence could not be true if the second were not true; if the president were not dead, then whatever it is that happened to him would not have counted as a (successful) assassination. Similarly, unlike implicatures, entailments cannot be cancelled; there is no qualification that one could add to "The president was assassinated" which would cause it to cease entailing "The president is dead" while also preserving the meaning of the first sentence.

Implicature and implication

The specialized term implicature was coined by Paul Grice as a technical term in pragmatics for certain kinds of inferences that are drawn from statements without the additional meanings in logic and informal language use of implication.

Practical reason

"In theory, there is no difference between theory and practice. But, in practice, there is." -- Jan L. A. van de Snepscheut

In philosophy, practical reason is the application of reason to real-world decision-making (ie. deciding on a course of action). Contrast this with theoretical reason (often called speculative reason) which is concerned with absolute and universal truths. For example: deciding exactly how to build a telescope is practical reason, whereas deciding between two theories of light and optics is speculative reason.

In cognitive research, practical reason is the process of ignoring unproductive possibilities in favor of productive possibilities. It is considered a form of cognitive bias, because it is illogical. An example would be calling all hospitals to look for your missing child, but not checking morgues, as finding his corpse would be 'counter-productive.'

Presupposition

In linguistics, a presupposition is background belief, relating to an utterance, that:

• must be mutually known or assumed by the speaker and addressee for the utterance to be considered appropriate in context

• will generally remain a necessary assumption whether the utterance is placed in the form of an assertion, denial, or question, and

• can be associated with a specific lexical item or grammatical feature (presupposition trigger) in the utterance.

In pragmatics, a presupposition is an assumption about the world whose truth is taken for granted in discourse. Examples of presuppositions include:

• Do you want to do it again?

  • Presupposition: You have done it already, at least once.

• My wife has arrived.

  • Presupposition: The speaker has a wife.

Crucially, negation of an expression does not change its presuppositions: I want to do it again and I don't want to do it again both mean that the subject has done it already one or more times; My wife has arrived and My wife has not arrived both mean that the subject has a wife. In this respect, presupposition is distinguished from entailment and implication. For example, The president was assassinated entails that The president is dead, but if the expression is negated, the entailment is not necessarily true.