Validation of Computer Simulations from a Kuhnian Perspective

von Eckhart Arnold

1 Introduction
2 Kuhn's philosophy of science
3 A revolution, but not a Kuhnian revolution: Computer simulations in science
4 Validation of Simulations from a Kuhnian perspective
5 Summary and Conclusions

2 Kuhn's philosophy of science

A crucial aspect of Kuhn's concept of scientific revolutions is the alleged incommensurability of paradigms (Kuhn 1976, ch. 12, postscript 5.) (Sismondo 2007, ch. 2) (Bird 2013, sec. 4.3f.). Incommensurability means that theories rooted in different paradigms cannot easily be compared with respect to their scientific merits, because of

  1. methodological incommensurability, which means that the criteria of evaluation depend on and change with the paradigm,
  2. the theory-ladenness of observation, due to which an assessment based on empirical evidence may not be able to resolve the dispute,
  3. semantic incommensurability, which means that the differences of the respective conceptual reference frameworks and taxonomies may render the translation between the nomenclatures of different paradigms difficult and error-prone.

Kuhn did not go as far as the proponents of the strong programme of sociology of science who maintain that the resolution of interparadigm-disputes is primarily, if not exclusively, determined by social factors such as group allegiance and power-structures (Bird 2013, sec. 6.3). However, he did deny that the choice between different theories is guided by a scientific meta-method such as systematic falsification or by any other particular set of rules. In this respect one can describe Kuhn's stance as a mild relativism. Kuhn's relativism is restricted by his belief that a common ground for theory choice can still be found in such general characteristics as empirical accuracy, consistency, breadth of scope, simplicity or parsimony, fruitfulness for future research (Kuhn 1977, ch. 13). And he furthermore holds that the comparison and mutual evaluation of paradigms is possible on the pragmatic basis of their problem-solving capacity.

Although Kuhn regarded scientific revolutions and the paradigm shifts they bring about as scientifically perfectly legitimate processes, that is processes that are primarily driven by a scientific motivation and not just by social power, he nonetheless found that in almost any paradigm change some things get lost - if only that certain questions will not be considered worthwhile any more. An example is the question how physical bodies influence each other over a distance, which cannot be answered by Newton's theory of Gravity and therefore simply was not asked any more, although, before Newton it was considered important (Kuhn 1976, ch. 12). The phenomenon that accepted questions, problems and even solutions can become orphaned after a paradigm shift has subsequently been called Kuhn loss (Bird 2013, sec. 2).

Also, even though Kuhn allowed for paradigm-shifts to make sense scientifically, this does not always need to be the case, but one should expect that sometimes paradigm-shifts are primarily due to social factors. Not in the least because of the popularity of Kuhn's theory of scientific revolutions, it has become seductive for scientists to stage a paradigm shift to promote their scientific agenda. In order to distinguish illegitimate paradigm-shifs terminologically, the derogatory term scientific imperialism can be used, which has been coined to describe the take-over of a branch of science by a single paradigm (Dupre 1994) by unfair means. Following Kuhn's line of thought the problem solving capacity could be a criterion by which to qualify a paradigm shift as either legitimate or imperialistic. Because of the incommensurability issues described before, an objective judgment about this can, of course, be difficult.

A contemporary of Kuhn that is often mentioned in the same breath, is Paul Feyerabend, who is (in-)famous for the slogan “anything goes”. In popular folklore this is sometimes understood as meaning that Feyerabend advocated that in science any method is as good as any other. However, what Feyerabend actually demonstrated in his book “Against Method: Outline of an Anarchist Theory of Knowledge” (Feyerabend 1975) and other works was that even from the most humble historical beginnings, a serious scientific theory or school of thought can still emerge. Feyerabend's work gains its thrust from the fact that he can show that some of the game changers in the history of science such as, for example, Galileo's theory of motion, violated accepted scientific standards of their time (Feyerabend 1975, ch. 9). Just as Kuhn he denies that the historical development of science is or can be guided by methodological or epistemological rules. Similar to Kuhn, Feyerabend's philosophy has a certain relativistic flair, which Feyerabend other than Kuhn was ready to accept (Preston 2016, sec. 5).

Nonetheless, despite of what the subtitle of his major work suggests, Feyerabend's analyses do not warrant a strong relativism. Almost all of Feyerabend's examples concern theories that - later in their historical development - would be considered as scientific even by conventional standards. Thus, what we can learn from Feyerabend is a certain tolerance against the methodological chaos of new scientific approaches in their infant stages. This can be important, for example, when evaluating social simulations, which according to some authors suffer from a lack of proper empirical validation (Heath et al. 2009). The question is then not so much whether these simulations adhere to a particular scientific standard but rather whether the respective scientific community learns from its failure to do so and will be able to develop appropriate methodological standards in the future.

Another point that deserves clarification, because it is - at least in the philosophical discussion - almost habitually mentioned in context with Kuhn, is the Duhem-Quine-thesis (Harding 1976). The Duhem-Quine-thesis draws on the fact that if the logical consequence of a whole system of premises turns out to be false then it is still unclear which one or more of the premises are false.[2] This means that if a theory is empirically disconfirmed, we do not (yet) know which part of the theory is wrong. The Duhem-Quine-thesis can be seen as supporting a certain degree of arbitrariness, if not relativism in theory choice. And it corresponds well to Kuhn's view that the way scientists cope with anomalies is not strictly guided by methodological rules. It may be a matter of creative choice. As we shall see later, this choice is in practice much less arbitrary than it may appear in the formal logical representation of a theory as a system of propositions.

Despite all reservations, Kuhn's picture of the history of science is still one of linear development, where normal science and revolutionary phases follow each other in time. For Kuhn the prolonged co-existence of several competing paradigms was the mark of a pre-scientific stage where much intellectual energy is wasted in disputes between rivaling schools of thought. Recent research, however, has emphasized that the co-existence of different paradigms within one and the same science is much too common to be dismissed as pre-scientific (Kornmesser 2014, Schurz 2014). This is particularly true of the social sciences, where hardly ever one paradigm can claim to solve all puzzles so successfully that it is able to gather the entire scientific community under its flag. That Kuhn may have underestimated the amount of co-existence of paradigms in science does not invalidate his analyses, though. The concepts of normal science and scientific revolutions can still be employed as ideal-types to characterize the scientific proceedings within an established paradigm on the one hand and the discourse between different co-existing paradigms on the other hand.

[2] See also chapter 39 (Lenhard 2019) in this volume.

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