Reducing Contrastive Knowledge
According to one form of epistemic contrastivism, due to Jonathan Schaffer, knowledge is not a binary relation between an agent and a proposition, but a ternary relation between an agent, a proposition, and a context-basing question. In a slogan: to know is to know the answer to a question. I argue, first, that Schaffer-style epistemic contrastivism can be semantically represented in inquisitive dynamic epistemic logic, a recent implementation of inquisitive semantics in the framework of dynamic epistemic logic; second, that within inquisitive dynamic epistemic logic, the contrastive ternary knowledge operator is reducible to the standard binary one. The reduction shows, I argue, that Schaffer’s argument in favor of contrastivism is compatible with a binary picture of knowledge. This undercuts the force of the argument in favor of contrastivism.
I would like to thank Johan van Benthem, Ray Briggs, Ivano Ciardelli, Krista Lawlor, Lisa Modifica, Jonathan Schaffer and and two anonymous referees of this journal for many helpful comments, suggestions and corrections on earlier versions of this article.
- Baltag, A., & Renne, B. (2016). Dynamic epistemic logic. In E. N. Zalta (Ed.), The Stanford encyclopedia of philosophy. Winter 2016 edition.Google Scholar
- Ciardelli, I. (2016). Questions in logic. Ph.D. Thesis, University of Amsterdam.Google Scholar
- Ciardelli, I., Groenendijk, J., & Roelofsen, F. (2018). Inquisitive semantics. In Oxford surveys in semantics and pragmatics. Oxford: Oxford University Press.Google Scholar
- Cross, C., & Roelofsen, F. (2016). Questions. In E. N. Zalta (Ed.), The Stanford encyclopedia of philosophy. Spring 2016 edition.Google Scholar
- Groenendijk, J. (2007). The dynamics of inquiry. In Central APA. Handout.Google Scholar
- Lewis, D. (1982). Whether’ report. In T. Pauli (Ed.), 320311: Philosophical essays dedicated to Lennart Åqvist on his fiftieth birthday (pp. 194–206). Uppsala: University of Uppsala Press.Google Scholar
- Roelofsen, F. (2015). The semantics of declarative and interrogative lists. Manuscript, ILLC University of Amsterdam.Google Scholar
- Rysiew, P. (2011). Epistemic contextualism. In E. N. Zalta (Ed.), The Stanford encyclopedia of philosophy. Winter 2011 edition.Google Scholar
- Schaffer, J. (2005). Contrastive knowledge. In T. S. Gendler & J. Hawthorne (Eds.), Oxford studies in epistemology (Vol. 1, p. 235). Oxford: Oxford University Press.Google Scholar
- van Ditmarsch, H., van der Hoek, W., & Kooi, B. (2007). Dynamic epistemic logic. In Synthese library. Netherlands: Springer.Google Scholar
- van Gessel, T. (2018). Action models in inquisitive logic. Synthese. https://doi.org/10.1007/s11229-018-1886-5.