The purpose of this 3 hour workshop is to assist those already familiar with classical propositional logic to acquire the necessary skills in order to reconstruct natural language arguments, particularly the degree to which a premise or conclusion is accepted, by means of (subjective) probabilities. The main learning outcome is the participants’ (improved) ability to engage with the literature on the Bayesian approach to natural language argument so as to possibly contribute to it. The workshop provides participants with access to recent developments in formal philosophy that can facilitate interdisciplinary research and new research options particularly for those who teach argumentation analysis and evaluation.

During the morning, participants are introduced (i) to Bayes’ theorem, which serves as a normative standard for evaluating arguments as to being strong or weak ones, and to (ii) formal measures used for this purpose, namely measures of argument strength and argument force. In exemplary manner, participants employ their newly acquired knowledge during the afternoon session to the analysis of selected instances of classical fallacies. This serves to better understand how the Bayesian approach to natural language argument models the way in which their fallaciousness stands or falls with assumptions that can be rendered precise by means of employing subjective probabilities. At the end, future research issues are briefly presented, and occasion for group discussion is provided.

Key references
Bayes, T., & Price, R. (1763). An Essay towards solving a Problem in the Doctrine of Chance. By the late Rev. Mr. Bayes, communicated by Mr. Price, in a letter to John Canton, M. A. and F. R. S. Philosophical Transactions of the Royal Society of London, 53, 370–418.

Evans, J.S.T.B. (2002). Logic and Human Reasoning: An Assessment of the Deduction Paradigm. Psychological Bulletin, 128(6), 978–996.

Floridi, L. (2009). Logical fallacies as informational shortcuts. Synthese, 167, 317–325.

Fitelson, B. (2001). Studies in Bayesian confirmation theory. Dissertation, University of Wisconsin at Madison. http://fitelson.org/thesis.pdf.

Hahn, U., and Oaksford, M. (2006). A Bayesian Approach to Informal Reasoning Fallacies. Synthese, 152, 207–223.

Hahn, U., Harris, A.J.L, and Corner, A. (2009). Argument Content and Argument Source: An Exploration. Informal Logic, 29 (4), 337–367.

Korb, K. (2004). Bayesian informal logic and fallacy. Informal Logic, 23(2), 41–70.

Oaksford, M. and Chater, N. (2009). Precis of Bayesian rationality: the probabilistic approach to human reasoning. Behavioral and Brain Sciences, 32, 69-120.

Zenker, F. (ed.) (2013). Bayesian Argumentation: The Practical Side of Probability (Synthese Library, Vol. 362). Dordrecht: Springer.

Zenker, F. (2015). Denying the Antecedent Probabilized: a Dialectical View. In: Eemeren, F.H. van, Garssen, B., Godden, D, and Mitchell, G. (eds). Proceedings of the 8th International Conference of the International Society for the Study of Argumentation (ISSA), July 2014 (pp. xx–xx). Amsterdam: SicSat (forthcoming).

Godden, D.M., and Zenker, F. (2015). Denying antecedents and affirming consequents: The state of the art. Informal Logic, 88-134.