The informativeness principle is an implicature in which the addressee is licensed to apply his or her knowledge of the world to infer an implicature that is informationally stronger than the actual utterance.
This principle, in addition to the cooperative principle and conversational maxims, enables the addressee to resolve apparent conflicts with the quantity maxim.
- The utterance He turned on the switch and the motor started generally implicates the stronger utterance He turned on the switch and this caused the motor to start.
- The quantity maxim would ordinarily disallow such a strong implicature on the assumption that the cooperative speaker is making his contribution adequately informative. However, the informativeness principle allows the addressee to infer the implicature based on the knowledge of how motors start.