Conditional logics are logics which augment traditional logical implication with modal operators corresponding to other notions of condition (for example, the causal conditional $A\; \square\!\!\!\!\to B$ reads "$A$ causes "B", or probabilistic conditioning "$A|B$", which reads "$A$ given $B$").

Typically these logics are studied model-theoretically, but I've wondered about their applications to programming language design (for example, to type imperative actions).

I'd appreciate references to their proof theory (ie, sequent calculus/natural deduction), or to programming languages with types based on these kinds of modal operators.


EDIT: The Stanford Encyclopedia of Philosophy has a nice introduction to the subject.

  • $\begingroup$ Hello Neel, this sounds quite interesting. I tried to Google "conditional logics" but couldn't find much. Could you please suggest an introductory paper or something to know more about CL? thank you $\endgroup$
    – OldFella
    Commented Apr 12, 2011 at 9:58

2 Answers 2


Check these references:

Programming languages CondLP and CondLP+:

Gabbay, Giordano, Martelli, Olivetti, Sapino, Conditional reasoning in logic programming, Journal of Logic Programming, Volume 44, Issues 1-3, 1 July 2000, Pages 37-74

Claudia, Oliveira, The implementation of CondLP, Lecture Notes in Computer Science, 1996, Volume 1085/1996, 713-715

Gabbay, Giordano, Martelli, Olivetti, Conditional logic programming, Proc. 11th Int. Conf. on Logic Programming, Santa Margherita Ligure, pages 272–289, 1994.

References to proof theory:

Olivetti, Pozzato, Schwind, A sequent calculus and a theorem prover for standard conditional logics, Journal ACM Transactions on Computational Logic (TOCL), Volume 8 Issue 4, August 2007

  • $\begingroup$ Thanks, this looks very interesting! I was hoping to see some functional or imperative languages rather than logic languages, though. $\endgroup$ Commented Apr 12, 2011 at 13:38

Church might be the kind of thing you are looking for -- it is functional (scheme derivative), but is designed with a probabilistic semantics, and implements conditional probabilities using "query" for doing Bayesian inference. Discussion of conditioning in Church. This is (as I understand it) more or less the main operation in most Church programs.

To Matteo Mio: you might also be interested in Graham Priest's book, "An introduction to non-classical logic", which is centered around defining different types of conditionals.


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