Roland Poellinger, Postdoctoral Researcher at the Munich Center for Mathematical Philosophy (MCMP) visited Professor Jan-Willem Romeijn, Head of the Department of Theoretical Philosophy at the University of Groningen, The Netherlands, from April to May, 2017.

Similarity structures everywhere.Similarity structures everywhere.

When I was making plans to spend an intense research visit abroad in Spring 2017, there would not have been a better place for me than Groningen: What unites philosophers in Munich and Groningen is a strong focus on formal methods and Bayesian reasoning. In much of my work, Bayesian networks are the means of choice. Using such nets, I have looked at causal decision theory and paradox in causal reasoning. I developed ideas for integrating causal and non-causal knowledge in an extension of the Bayes net framework, and more recently I have become highly interested in using Bayes nets for reconstructing analogical arguments in science and for making explicit how analogies can help confirming scientific hypotheses. I guess, my interest in paradox also fueled my interest in analogy: In a recent book, Paul Bartha states that “[f]or Bayesians, it may seem quite clear that an analogical argument cannot provide confirmation” (Bartha, 2010). Well, that did not seem so clear to me. Bartha argues that any analogical argument E expressing the analogy relation between source and target domain is – if it is meant to support hypothesis H – necessarily already contained in one’s background knowledge K (as old evidence), such that Pr( H | E & K ) = Pr( H | K). The equality sign shouts at the Bayesian: no confirmation here! I do agree with the argument. But: Shouldn’t the powerful Bayesian framework be able to capture scientific strategies based on analogical reasoning? (See also Beebe & Poellinger, forthcoming) Many, many analogical arguments have proven fruitful for discovery and hypothesis testing in many, many research contexts: Physics, econometrics, medicine, etc. And in pharmacology – the current focus of my work – analogical arguments surface in deep and difficult questions about extrapolation. In his famous and influential paper “The Environment and Disease: Association or Causation?” (1965), Sir Austin Bradford Hill lists analogy as one of his famous guidelines towards an informed assessment of potential causes in epidemiology:

In some circumstances it would be fair to judge by analogy. With the effects of thalidomide and rubella before us we would surely be ready to accept slighter but similar evidence with another drug or another viral disease in pregnancy.

A recent paper by Landes, Osimani, and Poellinger (2017) explores the possibility of amalgamating all available, potentially heterogeneous evidence in a Bayesian reconstruction of scientific inference for the integrated probabilistic assessment of a drug’s causal side-effects: In this framework, a scientific hypothesis (i.e., a causal claim) is supported by some evidential report, if this evidence is deemed relevant to the hypothesis – most importantly, if study and target can be called analogous.

With many ideas (and many questions) about how to relate formal explications of similarity, analogy, extrapolation, and confirmation, I was more than happy to visit Prof. Jan-Willem Romeijn and his group at the Department of Theoretical Philosophy at the University of Groningen in April and May, 2017. Not only did my project benefit greatly from Jan-Willem Romeijn’s expertise in Bayesian reasoning and statistical methodology, I was also invited to present my project and speak about analogical inference patterns (see Poellinger, forthcoming) at the workshop on “Causality in Psychological Modeling” (15 May, 2017). This event was co-organized by Jan-Willem Romeijn and Markus Eronen (Groningen/Leuven) and featured Laura Bringmann (UG) Denny Borsboom (UvA), as well as Naftali Weinberger (Tilburg). Highly interesting discussions at the overlap of Bayesian reasoning, causal modeling, statistical methodology, and psychometrics are to be continued – which I am very much looking forward to.

I am thankful to Richard Pettigrew, the Leverhulme Trust, and the ERC research project “Philosophy of Pharmacology” (grant 639276; principal investigator: Barbara Osimani) for making this exchange happen, and for sparking many ideas I brought back home.


Bartha, P. F. A. (2010): By Parallel Reasoning: The Construction and Evaluation of Analogical Arguments, Oxford University Press.

Beebe, C. & Poellinger, R. (201X): Confirmation from Analog Models. (submitted)

Hill, A. B. (1965): The Environment and Disease: Association or Causation? Proceedings of the Royal Society of Medicine, 58(5), 295–300.

Landes, J., Osimani B., Poellinger R. (2017): Epistemology of Causal Inference in Pharmacology. Towards a Framework for the Assessment of Harms. European Journal for the Philosophy of Science. DOI:

Poellinger, R. (201X) Analogy-Based Inference Patterns in Pharmacological Research. In: La Caze, A. & Osimani, B (eds.): Uncertainty in Pharmacology: Epistemology, Methods, and Decisions. Boston Studies in Philosophy of Science. Springer (forthcoming).