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  • Marcel Kertels

    Theoretische Philosophie

    © Universität Bielefeld

Marcel Kertels, M.A.

Doctoral student/Research assistant at the chair of theoretical philosophy

© Universität Bielefeld

Department of Philosophy
PO Box 10 01 31, 33501 Bielefeld

phone: +49 521 106-67106  
office: X A4-200

office hours: by arrangement

Research Project: A Modal Theory of Indicative Conditionals (working title)

The meaning of conditionals is a matter of controversial discussion since antiquity. With respect to so-called subjunctive conditionals like (to use Adams' well-worn examples)

"If Oswald hadn't killed Kennedy, someone else would have." ,

David Lewis provided a (controversial) standard with his book Counterfactuals in 1973. With respect to so-called indicative conditionals like

"If Oswald didn't kill Kennedy, someone else did.",

however, there are still several theories under discussion. The proposals range from truth-functional approaches to approaches that deny that indicative conditionals have truth values.

In my thesis, I advocate a possible worlds semantics similar to Lewis' semantics for counterfactual conditionals according to which indicative conditionals have truth values but are not truth-functional. Thus, on the one hand, a possible worlds semantics for indicative conditionals has the advantage to evade classical problems for other approaches like the paradoxes of material implication. On the other hand, a possible worlds semantics for indicative conditionals yields, together with Lewis' theory of counterfactual conditionals, a uniform theory of conditionals.

Challenges for a possible worlds semantics are in particular:

  • to clarify which possible worlds are relevant; a central issue here is whether epistemic factors like the speaker's knowledge influence the relevance of worlds,
  • to deal with rigidifying expressions in indicative conditionals; one approach here is to draw on two-dimensional semantics and to regard the primary intension as relevant in indicative conditionals,
  • to take the probabilities of indicative conditionals into account; the probability of the indicative conditional expressed by "if A, then C" is usually regarded as the conditional probability of C given A, but for formal reasons this conditional probability cannot be the probability of truth of the conditional.


You can find my courses here.

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