Modality (philosophy)

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In philosophy, modality describes the way something is, happens or is thought.

Concept and types of modality

Modalities in the strict sense

In the narrower, classic sense, the term modality denotes the alethic (truth-related) modality: in ontological terms, it is the way in which a state of affairs exists or, more logically, the truth of statements .

In addition to the simple (factual) truth, a distinction is usually made between necessity , possibility and impossibility and contingency .

The concept of the (alethic) modality is already used by the commentators on Aristotle .

According to Kant , categories of modality are possibility, reality and necessity, to which the modality of judgments (problematic (possible), assertoric (real), apodictic (necessary)) should correspond.

Leibniz differentiates between four basic categories of types of statements or facts : necessary, possible, impossible and contingently true (actual).

Classical theorists as well as modern semantics , philosophy of language , logic (especially modal logic ) and ontology have proposed different theories about the nature of these statements and their truth makers .

Modalities in the broader sense

In addition to the alethic modalities mentioned, one also speaks of the modalities in the broader sense and means (among other things) the ways in which a statement can be true in relation to the knowledge of the telling, the time or the ought. This covers the doxastic (epistemic), temporal or deontic modalities.


The different modalities can be traced back to each other, are in an analogous relationship and justify different modal logics :

formula Modal logic i. e. S. Deontic logic Temporal logic Doxastic logic
p It is possible that p It is permissible that p p applies sometime in the future (past) I think it is possible that p
p It is necessary that p It is imperative that p p is always valid in the future (past) I consider it certain that p

Modality and Possible Worlds Theory

Following Leibniz, Rudolf Carnap ( Meaning and Necessity 1947), Saul Kripke and David Kellogg Lewis suggested that modal statements should be understood as statements about or in possible worlds . A necessary truth is true in all of these worlds, a possible truth in at least one. These worlds, according to Lewis, are real and even concrete objects, not just concepts in the mind or abstract universals. This ontologically demanding option has theoretical advantages because it enormously simplifies the semantic evaluation of modal statements . In addition, there are ontologically irreducible relationships between these possible worlds, which makes the evaluation of conditionalities (if ... then ...) and v. a. of counterfactual conditionalities (if it weren't… then…) are very elegantly simplified. Nevertheless, many ontologists are not ready to add so many additional irreducible objects to their ontological inventory. Some therefore try to maintain the theoretical elegance of many-worlds semantics, but propose anti- realistic substitute theories regarding the ontological dignity of these worlds.

Theories about actuality

Theories about actuality are a separate subject area in these debates : What is constitutive for the fact that the actual world is the actual and no other possible world? A much-discussed proposal understands "aktual" as indexical expression when: I say that a situation is aktual, then I say that he listened to the world that I (the speaker) inhabit (and I now their inventory with your finger show can ). (According to Lewis, who takes this position, there is no identity of objects across different worlds (so-called transworld identity), only counterparts; there is therefore only one speaker.) Alternatively, for example, that world can be determined as actual, in which we do the evaluation of an utterance .

See also


  • Nicolai Hartmann: Possibility and Reality. de Gruyter, Berlin 1938.
  • Robert Merrihew Adams: Theories of Actuality. In: Noûs , 8/3 (1974), pp. 211-231, also in: Loux 1979.
  • John Divers: Possible Worlds. Routledge, 2002.
  • David Kellogg Lewis : On the Plurality of Worlds. Blackwell, 1986.
  • Michael J. Loux (Ed.): The Possible and the Actual. Cornell University Press, Ithaca NY 1979.
  • Uwe Meixner: Modality. Possibility, necessity, essentialism . Klostermann, Frankfurt am Main 2008, ISBN 978-3-465-04050-7 .
  • Alvin Plantinga : Actualism and Possible Worlds. In: Theoria 42 / 1-3 (1976), pp. 139-160, also in: ders .: Essays in the Metaphysics of Modality. Matthew Davidson (Ed.): Oxford University Press, New York NY 2003, pp. 103–121 and also in Loux 1979.
  • Alvin Plantinga: Two Concepts of Modality: Modal Realism and Modal Reductionism. In: James E. Tomberlin (ed.): Philosophical Perspectives , 1 (1987), Atascadero, CA: Ridgeview, pp. 189-231, also in: Plantinga 2003, 192-228.
  • Alexander R. Pruss: The Actual and the Possible . In: Richard M. Gale (Ed.): The Blackwell Guide to Metaphysics . Blackwell 2002.
  • Ted Sider : Reductive Theories of Modality (PDF; 310 kB). In: MJ Loux, DW Zimmerman (Eds.): The Oxford Handbook of Metaphysics. OUP 2003.
  • Robert Stalnaker : Possible Worlds. In: Noûs , 10/1 (1976), pp. 65-75 also in Loux 1979.
  • Peter van Inwagen : Two Concepts of Possible Worlds. In: Peter A. French, Theodore E. Uehling, Jr., Howard K. Wettstein (Eds.): Midwest Studies in Philosophy 11 (Studies in Essentialism), University of Minnesota Press, Minneapolis MN 1986, pp. 185-213; also in van Inwagen 2001, pp. 206–242.
  • Peter van Inwagen: Ontology, Identity, and Modality : Essays in Metaphysics. Cambridge Studies in Philosophy. Cambridge University Press, Cambridge 2001.

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