A post by Alice Murphy.
Is there a role for aesthetic judgements in science? One aspect of scientific practice, the use of thought experiments (TEs), has a clear aesthetic dimension. TEs are creatively produced artefacts that are designed to engage the imagination and are used to motivate, undermine, explain or clarify theories. Comparisons have been made between scientific (and philosophical) TEs and other aesthetically appreciated objects, namely works of art. In particular, TEs are said to share qualities with literary fiction as they invite us to imagine a fictional scenario and often have a narrative form (Elgin 2014). It is therefore unsurprising that TEs should bear significant aesthetic features. But philosophical discussions of aesthetics in science have focused mainly on the epistemic role of beauty and elegance when it comes to theories and mathematical proofs and TEs have been widely overlooked.
Nevertheless, TEs are also referred to as beautiful or elegant. Take Galileo’s famous falling bodies, referred to as ‘the most beautiful thought experiment ever devised’ (Brown 2004, 24). It is also second on a poll conducted by Physics World of the ten most beautiful experiments of all time (Crease 2002). In 2012, edge.org conducted a survey which asked 192 people including scientists and philosophers what their “favourite deep, elegant or beautiful explanation” is. As Stuart points out, 21 of the answers given were TEs and a further 8 were ‘imagination-based inferences that any broad-minded characterization of thought experiments should include’ (2017, 530). Physicist Sean Carroll’s favourite deep, elegant or beautiful explanation, for instance, is Einstein’s TE that was used as part of his explanation of why gravity is universal, what Einstein called the “happiest thought” of his life. Further, some TEs have negative aesthetic evaluations e.g. Darwin’s whale TE which fails to explain natural selection by describing how whales could have evolved from bears, and was described by Agassiz as “truly monstrous” (Stuart 2016).
Why are some TEs considered beautiful? It may be because they invite us to imagine a phenomenon or a set of circumstances that is aesthetically interesting or pleasing, such as Einstein’s TE where we imagine the experience of chasing a light beam. Another way the beauty of TEs is characterised (which is also the way in which theories and concrete experiments are often considered beautiful) is in terms of an “optimal use of minimal material”. For Brown, Galileo’s TE is beautiful because it is ‘brilliantly original and as simple as it is profound’ (2004, 24). Similarly, Sean Carroll states ‘Einstein, in his genius, realized the profound implication’ of the situation described in the TE.
This leads us to a worry. When scientists or philosophers of science describe certain TEs using aesthetic terminology, are they just claiming that the TE is successful or unsuccessful? The thought is that when Galileo’s TE is described as “beautiful” or Darwin’s as “monstrous”, the application of aesthetic terms is merely metaphorical. On the other hand, if judgements of “beauty”, “elegance” and so on are genuinely aesthetic, i.e. their use is literal, and they cannot be reduced to epistemic features, then we ought to question whether they have an important part to play in the scientific context. Any account of the aesthetics of science must provide reasons as to why we should take these descriptions as genuinely aesthetic whilst maintaining that they have a meaningful role.
One way to defend their role is by thinking about aesthetic features in science in terms of the appropriateness of form to content. On this view, aesthetic value has to do with the way in which epistemic content (however you want to cash this out, say in terms of knowledge or understanding) is conveyed. This would fit well with theories of functional beauty in aesthetics which argue that fitness for function is a source of aesthetic value. As we’ve seen, the beauty of TEs appears to lie in their ability to evaluate, explain or help us understand something profound based on a simple scenario. In addition, beautiful or elegant TEs are those in which the particular details have been carefully selected. The value of TEs, then, is that they provide us with a scenario that makes something complex easy to visualise and to understand and thus, I argue, their form is crucial for grasping their content.
Understanding has recently become a topic of significant interest in the philosophy of science, and there are a number of accounts that can be utilised to illuminate how TEs contribute to understanding. We can look to one recent view developed by de Regt that focuses on theories. The key notion for de Regt is “intelligibility”; ‘the value that scientists attribute to the cluster of qualities of a theory (in one or more of its representations) that facilitate the use of the theory’ (2017, 40). While not essential for achieving understanding, one of the qualities included in this cluster is visualisability which de Regt argues is an effective tool for understanding. Briefly put, de Regt’s view is that scientists often prefer visualisable over abstract theories and further find pictorial representations useful in understanding. He further states that this is to be expected given that ‘seeing is for humans plausibly the most important way of grasping the world around us’ and so ‘when we want to extend our grasp of the world beyond what we observe directly, we prefer to rely on our well-developed visual skills and employ visualization as a tool for understanding’ (257).
De Regt offers an account of what it means for a theory to be intelligible. But one way in which scientists make theories intelligible is through TEs, and TEs are good at facilitating such understanding because of their aesthetic properties. TEs are performed in the imagination, and we can use them most effectively when their particulars are presented to us in an elegant manner. TEs that are e.g. cluttered or clumsy would be less useful due to the role that they are supposed to play in science, especially their role in pedagogy.
We can see this by returning to Galileo’s falling bodies. It is through the introduction of the particular objects that we engage with the TE, and therefore come to understand what the TE and the relevant theorising is about. In Galileo’s case, reference to the two balls attached together is an integral part of the presentation. Therefore, the particulars are not “irrelevant”; without them, some TE scenarios will not be properly visualisable. Furthermore, if we look at the context in which The Two Dialogues was written, Galileo was writing to appeal not only to a scientific but also to the public community. The formulation is suited to that audience and enhances the accessibility of the TE scenario. This contributes to the cognitive force of the TE, hence meeting de Regt’s use criteria.
There is clearly more to be said on this topic. Some further considerations are the following: Can the beauty of TEs contribute to the force of misleading cases? Is there a change in what makes a TE beautiful or elegant from era to era, and does this alter across the sciences? Finally, is there variation with regards to the effectiveness of aesthetic qualities or formulation according to the role the TE is playing, and the type of imagination it invites?
I hope to have shown that by characterising aesthetics of science in terms of the appropriateness of form to content, we can defend the role of aesthetic features in science without reducing them to epistemic features. This is because appropriateness of form to content is an aesthetic property that contributes to understanding. As a consequence, accounts of scientific understanding that highlight the role of the imagination ought to pay attention to the aesthetics of science, and TEs demonstrate how such aesthetic considerations are an important aspect of scientific practice.
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Thanks to Steven French, Aaron Meskin, Mike Stuart and those who gave comments at the British Society for Philosophy of Science 2019 conference in Durham for helpful feedback.
 Some of this post overlaps with Murphy, Alice, ‘The Aesthetic and Literary Qualities of Scientific Thought Experiments’, in French, S. and Ivanova, M. (eds) Aesthetics of Science: Beauty, Imagination and Understanding, Routledge (forthcoming).
 Darwin’s thought experiment, which appeared in The Origin of Species but was removed from later editions, goes as follows: "In North America the black bear was seen by [the explorer Samuel] Hearne swimming for hours with widely open mouth, thus catching, like a whale, insects in the water. Even in so extreme a case as this, if the supply of insects were constant, and if better adapted competitors did not already exist in the country, I can see no difficulty in a race of bears being rendered, by natural selection, more and more aquatic in their structure and habits, with larger and larger mouths, till a creature was produced as monstrous as a whale."
 This phrase is taken from Parsons and Rueger who argue that the beauty of concrete experiment lies in ‘the simplicity of the arrangement, its economy, or its ability to unify several tasks in one display’ (2000, 412). A clear feature that is part of the beauty of theories is also economy; the theory postulates a small number of hypotheses or axioms which provides many successful predictions, or can explain a wide range of phenomena (see e.g. Ivanova, 2017).
 The issue has been raised in the context of the aesthetics of theories by Todd who claims that ‘what appears to be aesthetic claims may often be, if perhaps not always are, really masked ‘epistemic’ functional ones’ (2008, 77).
 Todd (2008) points towards this as a possible direction for aesthetics of science given the worries above.
 See e.g. Parsons and Carlson (2008). For discussion of functional beauty in mathematics, see Dutilh Novaes (2019) and Bueno (2009).
 What type of imagination is involved in TEs? Many emphasise the role of imagery. A recent account developed by Salis and Frigg (forthcoming) argues that only a propositional form is required. Elsewhere, I develop a pluralist stance; different TEs engage different types of imagination. Here, the claim is that visualisation can be effective in science. This holds regardless of whether TEs can ultimately be reconstructed into propositional form.
 See Stuart (2018) for an account of how TEs increase understanding.
 Here I have in mind Norton’s view that TEs ‘are arguments which (i) posit hypothetical or counterfactual states of affairs and (ii) invoke particulars irrelevant to the generality of the conclusion’ (1991, 129).
 This allows us to resist Currie’s view (in the context of the comparisons between models and literary fiction) that ‘Models [and TEs] are not dependent for their value in learning on any particular formulation; rather they depend on their capacity to get good predictive or explanatory results or to achieve some other epistemic aims’ (2016, 305).
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“Edge.org.” Accessed August 8, 2019. https://www.edge.org/responses/what-is-your-favorite-deep-elegant-or-beautiful-explanation.
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Parsons, G. and A. Carlson. Functional Beauty. Oxford, New York: Oxford University Press, (2008).
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