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Debate over QCA's three solution types intensifies at Cologne meeting

Posted 11/6/2018

From 25-26 April 2018, about a dozen scholars working on topics around QCA gathered at the Cologne Center for Comparative Politics at the University of Cologne, Germany, to present their work and discuss that of others. Ingo Rohlfing and his team organized this meeting.   

After COMPASSS shied away from entering into an open debate on QCA's three solution types (conservative, intermediate, parsimonious) at their QCA Expert Workshop in Zurich in December 2017, Adrian Dusa presented a working paper that supposedly shows how Baumgartner and Thiem (2017) have run into a series of logical fallacies and that their simulations are deficient. This working paper follows COMPASSS' Rejection Statement (see previous post), but now presents a scientific argument instead of just calling on researchers to ignore Baumgartner and Thiem (2017) and related works. 

Although Dusa's working paper has not yet been accepted at a journal, it has already been used by Carsten Schneider in his QCA course at the ECPR methods winter school and by reviewers of QCA submissions, and it is invoked by Adrian Dusa himself in public fora such as ResearchGate. Surprisingly, however, Dusa does not want to let the scientific community scrutinize his argument and refuses to release his working paper. An odd situation for science: Dusa and Schneider already shout out in public that they have evidence that Baumgartner and Thiem (2017) are wrong, but they do not want anybody to get the chance to evaluate this "evidence".

At the Cologne meeting, I had the chance to evaluate it myself, and was surprised how little substance Dusa's paper had. In fact, it was so larded with mistakes that I can only summarize the main ones here.

  1. Dusa did not notice that the Boolean expression (A → C) + (B → C) is not the same as A + B → C [for A = 1, B = 0, C = 0; and for A = 0, B = 1, C = 0, these functions' truth values are different].
  2. Dusa interpreted X → Y as meaning that X is assumed to be true [any statement of the form X → Y is true whenever X and Y are true, or whenever X is false].
  3. Dusa cited Mackie in support of his argument, but conveniently re-interpreted the passages he took from Mackie [for example, Dusa simply dropped Mackie's notion of "elliptical knowledge", that is, the idea that less can be inferred with fewer data, to argue that parsimonious solutions are often wrong].
  4. Dusa thought that, when there are no logical remainders, conservative and parsimonious solutions may be different [when a truth table shows no logical remainders, all of QCA's three solution types will always produce exactly the same output].
  5. Dusa argued that the Quine-McCluskey algorithm does not, by default, use logical remainders [McCluskey, Edward J. 1965. Introduction to the Theory of Switching Circuits. Princeton: Princeton University Press. Page 126: "Any d terms [don't cares, i.e. logical remainders] which are present are treated as 1 terms in forming the prime implicants"].   

If you like to scrutinize my full review of Dusa's argument, please send a private request to me and I will make it available to you. Contrary to Dusa, I believe that science is best served by full transparency. 



  • Baumgartner, Michael and Alrik Thiem. 2017. "Often trusted but never (properly) tested: Evaluating Qualitative Comparative Analysis." Sociological Methods & Research. Advance online publication. DOI: 10.1177/0049124117701487.