Linguistics and Philosophy

, Volume 1, Issue 3, pp 337–355 | Cite as

What ‘must’ and ‘can’ must and can mean

  • Angelika Kratzer


In this paper I offer an account of the meaning of ‘must’ and ‘can’ within the framework of possible worlds semantics. The paper consists of two parts: the first argues for a relative concept of modality underlying modal words like ‘must’ and ‘can’ in natural language. I give preliminary definitions of the meaning of these words which are formulated in terms of logical consequence and compatibility, respectively. The second part discusses one kind of insufficiency in the meaning definitions given in the first part, which arise from the ‘ex falso quodlibet’ paradox of logical consequence. In stepwise fashion, I make an attempt to avoid most of the consequences of this paradox for the meaning definitions of ‘must’ and ‘can’.


Artificial Intelligence Natural Language Logical Consequence Relative Concept Computational Linguistic 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.


  1. Cresswell, M. J.: 1973, Logics and Languages. London: Methuen.Google Scholar
  2. Grabski, M.: 1974, Syntax und Semantik der Modalverben in Aussagesätzen des Deutschen. Dissertation, Universität Stuttgart.Google Scholar
  3. Kratzer, A.: 1976, ‘Was “können” und “müssen” bedeuten können müssen’. Linguistische Berichte 42.Google Scholar
  4. Lewis, D. K.: 1973, Counterfactuals. Oxford: Basil Blackwell.Google Scholar
  5. Rescher, N.: 1973, The Coherence Theory of Truth. Oxford: Clarendon Press.Google Scholar

Copyright information

© D. Reidel Publishing Company 1977

Authors and Affiliations

  • Angelika Kratzer
    • 1
  1. 1.Sonderforschungsbereich 99 “Linguistik”Universität KonstanzKonstanzGermany

Personalised recommendations