A Solution to Fitch' Paradox of Knowability

Part of the Logic, Epistemology, And The Unity Of Science book series (LEUS, volume 1)


There is an argument (first presented by Fitch), which tries to show by formal means that the anti-realistic thesis that every truth might possibly be known, is equivalent to the unacceptable thesis that every truth actually is known (at some time in the past, present or future). First, the argument is presented and some proposals for the solution of Fitch's Paradox are briefly discussed. Then, by using Wehmeier's modal logic with subjunctive marker (S5*), it is shown how the derivation can be blocked if one respects adequately the distinction between the indicative and the subjunctive mood. Essentially, this proposal amounts to the one by Edgington which was formulated with the help of the actuality-operator. Finally it is shown how the criticisms by Williamson against Edgington can be answered by the formulation of a new conception of possible knowledge that α (thereby α being in the indicative mood and thus referring to the actual world). This conception is based on the concept of same de re knowledge in different possible worlds.


Modal Logic Intuitionistic Logic Hybrid Logic Linguistic Community Subjunctive Mood 
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. Aristotle: 1975, Categories and De Interpretatione, translated with notes by J. L. Ackrill, Oxford, Clarendon Press.Google Scholar
  2. Barwise, J. and J. Etchemendy: 1987, The Liar. An Essay on Truth and Circularity, New York, Oxford, Oxford University Press.Google Scholar
  3. Barwise, J. and J. Perry: 1983, Situations and Attitudes, Cambridge, Bradford-MITGoogle Scholar
  4. Berkeley, G.: 1710, Treatise Concerning the Principles of Human Knowledge, Dublin.Google Scholar
  5. Blackburn, P.: 2001, ‘Modal Logic as Dialogical Logic’, in S. Rahman and H. Rückert (eds.), New Perspectives in Dialogical Logic, Synthese 127(1/2), 57–93.Google Scholar
  6. Blackburn, P., M. de Rijke and Y. Venema (eds.): 2001,Modal Logic, Cambridge, Cambridge University Press.Google Scholar
  7. Burge, T.: 1977, ‘Belief de re’, Journal of Philosophy 74, 317–338.CrossRefGoogle Scholar
  8. Crossley, J. and L. Humberstone: 1977, ‘The Logic of “Actually” ’, Reports on Mathematical Logic 8, 11–29.Google Scholar
  9. Davies, M. and L. Humberstone: 1980, ‘Two Notions of Necessity’, Philosophical Studies 38, 1–30.CrossRefGoogle Scholar
  10. Dummett, M.: 1977, Elements of Intuitionism, Oxford, Clarendon Press.Google Scholar
  11. Dummett, M.: 1978, Truth and Other Enigmas, London, Duckworth.Google Scholar
  12. Dummett, M.: 2001, ‘Victor's Error’, Analysis 61, 1–2.CrossRefGoogle Scholar
  13. Edgington, D.: 1985, ‘The Paradox of Knowability’, Mind 94, 557–568.CrossRefGoogle Scholar
  14. Fitch, F.: 1963, ‘A Logical Analysis of Some Value Concepts’, Journal of Symbolic Logic 28, 135– 142.CrossRefGoogle Scholar
  15. Hand, M. and J. Kvanvig: 1999, ‘Tennant on Knowability’, Australasian Journal of Philsopophy, 77, 422–428.CrossRefGoogle Scholar
  16. Hart, W.: 1979, ‘The Epistemology of Abstract Objects’, Proceedings of the Aristotelian Society Supplementary Volume, pp. 164–165.Google Scholar
  17. Hazen, A.: 1976, ‘Expressive Completeness in Modal Logic’, Journal of Philosophical Logic 5, 25–46.CrossRefGoogle Scholar
  18. Humberstone, L.: 1982, ‘Scope and Subjunctivity’, Philosophia 12, 99–126.CrossRefGoogle Scholar
  19. Humberstone, L.: 1985, ‘The Formalities of Collective Omniscience’, Philosophical Studies 48, 401– 423.CrossRefGoogle Scholar
  20. Kripke, S.: 1980, Naming and Necessity, Cambridge, Harvard University Press.Google Scholar
  21. Kvanvig, J.: 1995, ‘The Knowability Paradox and the Prospects for Anti-Realism’, Noûs 29, 481– 500.CrossRefGoogle Scholar
  22. Lindström, S.: 1997, ‘Situations, Truth and Knowability: A Situation-Theoretic Analysis of a Paradox by Fitch’, in E. Ejerhed and S. Lindström (eds.), Logic, Action and Cognition: Essays in Philosophical Logic, Dordrecht, Kluwer, pp. 183–209.Google Scholar
  23. McDowell, J.: 1984, ‘De re senses’, Philosophical Quarterly 34, 283–294.CrossRefGoogle Scholar
  24. Melia, J.: 1991, ‘Anti-Realism Untouched’, Mind 100, 341–342.CrossRefGoogle Scholar
  25. Perry, J.: 1979, ‘The Problem of the Essential Indexical’, Noûs 13, 3–21.CrossRefGoogle Scholar
  26. Perry, J.: 2001a, Knowledge, Possibility and Consciousness: the 1999 Jean Nicod Lectures, MIT Press.Google Scholar
  27. Perry, J.: 2001b, ‘Frege on Identity, Cognitive Value, and Subject Matter’, in A. Newen, U. Nort-mann and R. Stuhlmann-Laeisz (eds.), Building on Frege. New Essays about Sense, Content and Concept, CSLI publications, pp. 141–158.Google Scholar
  28. Rabinowicz, W. and K. Segerberg: 1994, ‘Actual Truth, Possible Knowledge’, Topoi 13, 101–115.CrossRefGoogle Scholar
  29. Sorensen, R.: 1988, Blindspots, Oxford, Oxford University Press.Google Scholar
  30. Tennant, N.: 1997, The Taming of the True, Oxford, Clarendon Press.Google Scholar
  31. Tennant, N.: 2001, ‘Is every Truth Knowable? Reply to Hand and Kvanvig’, Australasian Journal of Philosophy 79, 107–113.CrossRefGoogle Scholar
  32. Usberti, G.: 1995, Significato e Conoscenza: Per una Critica del Neoverificazionismo, Milano, Guerini Scientifica.Google Scholar
  33. Van Fraassen, B.: 1966, ‘Singular Terms, Truthvalue Gaps and Free Logic’, Journal of Philosophy 63, 481–494.CrossRefGoogle Scholar
  34. Wansing, H.: 2002, ‘Diamonds are a Philosopher's Best Friends. The Knowability Paradox and Modal Epistemic Relevance Logic’, Journal of Philosophical Logic 31, 591–612CrossRefGoogle Scholar
  35. Wehmeier, K.: 2003a, ‘Modality, Mood, and Descriptions’, unpublished manuscript, R. Kahle (ed.), Intensionality — An Interdisciplinary Discussion, AK Peters (Lecture Notes in Logic).Google Scholar
  36. Wehmeier, K.: 2003b, ‘World Travelling and Mood Swings’, in B. Löwe, T. Räsch and W. Malzkorn (eds.), Foundations of the Formal Sciences II, Kluwer (Trends in Logic).Google Scholar
  37. Williamson, T.: 1987, ‘On the Paradox of Knowability’, Mind 96, 256–261.CrossRefGoogle Scholar
  38. Williamson, T.: 1988, ‘Knowability and Constructivism’, The Philosophical Quarterly 38, 422–432.CrossRefGoogle Scholar
  39. Williamson, T.: 1992, ‘On Intuitionistic Modal Epistemic Logic’, Journal of Philosophical Logic 21, 63–89.Google Scholar
  40. Williamson, T.: 2000a, Knowledge and its Limits, Oxford University Press.Google Scholar
  41. Williamson, T.: 2000b, ‘Tennant on Knowable Truth’, Ratio, XIII(2), 99–114.CrossRefGoogle Scholar
  42. Wright, C.: 1993, Realism, Meaning and Truth, 2nd edn, Oxford, Blackwell.Google Scholar

Copyright information

© Springer Science+Business Media B.V. 2009

Authors and Affiliations

  1. 1.Department of Philosophy University of MannheimGermany

Personalised recommendations