thesis implicit in methods we actually use—might seem to shift the burden onto those methods themselves. Perhaps, one might argue, we should instead reject those methods rather than accept that beauty is relevant to theory evaluation. To counter this, I will provide a more direct argument for my thesis. This argument will have a transcendental structure: I will argue that my thesis is a necessary feature of the very nature of theorizing and explaining. Theories and explanations, by their very nature, are systematic. This fact, even before we develop any particular methods for evaluating theories and explanations, will entail that we will always be evaluating theories and explanations, in part, as systems. Theories and explanations are systems directed at a particular purpose: truth (or at least some other epistemic value). We will evaluate them in terms of how they achieve that purpose. But we also must evaluate them simply as systems. And this evaluation, I will argue, requires judgments of beauty. This transcendental argument will underpin my defense of the methods of reflective equilibrium and simplicity. But it will also provide a more general defense of my thesis: that beauty is relevant to theory evaluation. This transcendental argument will be developed in chapter 5.
This transcendental argument will conclude the argument for my thesis. My thesis is that judgments of beauty are part of how we evaluate theories; that a theory’s beauty is part of what makes it good. But there will remain several outstanding issues to be addressed. First, I will have spent some time thinking about the nature of explaining and theorizing, but there is a third related concept worth exploring: understanding. My core claim about explaining and theorizing is that they are necessarily systematic. This fits well with what is usually claimed is the nature of understanding as compared to knowledge: whereas knowledge is propositional, understanding is systematic. It will be important to speak to how my thesis relates to understanding. Second, the arguments I will develop in defense of this thesis are meant to be general and apply to theorizing of all kinds, but I will pay special attention to theorizing in philosophy. But this issue—the role of judgments of beauty in theorizing—is often specifically raised in the context of scientific theorizing. This is because scientific theorizing is supposed to be particularly empiricist or hardnosed; one might think that judgments of beauty can have utterly no place there. It will be important to speak to how my thesis relates to scientific theorizing. Third and finally, Rawls’ work—thinking about what desiderata a theory of justice must satisfy and giving a theory of justice in light of that—is an important foundation of this project. I have generalized Rawls’ attention to the methods of theorizing, including reflective equilibrium. But giving a theory of justice comes with its own special issues: a theory of justice is not merely supposed to explain something; it is supposed to provide a practicable framework for organizing society with an eye to peace, liberty, equality, and stability. It will be important to speak to how my thesis relates to these special issues in political theorizing. Each of these three topics could support a manuscript in their own right, but I will here only begin to explore them and flag them for further work. I will do this in the Coda.
Claiming that judgments of beauty are relevant to theory evaluation—that beauty is connected to truth—inevitably strikes many as wishy-washy or going soft on the hard business of discovering the truth in philosophy or science. But I will dispel that impression and argue that we must rely on our judgments of beauty when evaluating theories for truth. There is another, more ancient adage worth remembering: Pulchritudo splendor veritatis, “Beauty is the splendor of truth.”11 This adage does not say that beauty is truth, nor will I. I do not deny that we should reject a theory, no matter how beautiful, if it is not true. But our task when doing philosophy or science is to figure out which theories are true or otherwise epistemically good. And we don’t have direct access to that truth, antecedent to our judgments of beauty about theories, any more than we have direct access to that truth, antecedent to our judgments about fit with the data. Instead, finding that a theory is beautiful will be an important step toward finding that it is true, in the same way that finding that it fits with the data is an important step toward finding that it is true. A theory can be beautiful and yet not be true, just as a theory can fit with the data and yet not be true. Nevertheless, beauty and fit with the data are connected to truth and we must rely on them when forming our judgments about which theories we have reason to believe are true. Discovering whether a theory is true, which is indeed our ultimate goal, requires discovering whether it has some other property. And I will argue that one such other property, a middle term between theories and truth, is beauty.
NOTES
1 This is obviously meant to echo Rawls’ famous first lines of A Theory of Justice. Although the subject matter of this book is quite different from the questions Rawls addressed in his work, it will be clear that I am deeply indebted to him. I use the word “true” here only to echo Rawls. As I will discuss shortly, I only mean that theories must be principally evaluated according to epistemic values.
2 “Theory” is sometimes a fraught term, but I will be using it here merely to mean a “system of thought that explains some phenomenon.” Note that on this usage of the term systematicity is built into the concept and the purpose of theories is specified as explanation. Notice also that no degree of uncertainty is connoted by the term.
3 There are some debates over the exact nature of the epistemic value of theories. See, for example, Cartwright and McMullin (1984) and Slater (2008). And it is, of course, possible that there is more than one epistemic value that we use to evaluate theories. There is also the classic realist/antirealist dispute about how to understand the truth value of scientific theories. I mean the central claim here—that theories are principally evaluated according to epistemic goods—to be ecumenical with respect to these debates. I will continue to use “truth” as a stand-in for the core epistemic value of theories, but keep in mind that I mean this to be neutral with respect to debates over nature of the epistemic value of theories.
4 The arguments developed in this paragraph against the libertarian, radical egalitarian, and utilitarian theories of justice are, of course, the rudest sketches of arguments. It’s not my purpose here to seriously argue for one theory of justice over any other, we’re merely working through these sketched arguments to illustrate how the methods of theory evaluation we’ve considered work and how they can be deployed alongside one another in an attempt to get to a final answer as to which of the competitor theories is true. Rawls of course goes into much more detail in arguing for his theory. Indeed, he uses a more sophisticated method of theory evaluation—reflective equilibrium—to advance his preferred theory.
5 Fit with the data is closely related to Rawls’ method of theory evaluation, reflective equilibrium. For more on reflective equilibrium, see Brandt (1979), Brink (1987), Daniels (1979, 1980a, 1980b, 1983, 1996), DePaul (1986), Holmgren (1989), Mandle and Reidy (2013), Rawls (1971, 2001), and Sencerz (1986). Coherence is an important part of reflective equilibrium and is also sometimes discussed as method of theory evaluation unto itself. For more on coherence, see Bender (1989), DePaul (1987, 1993), Mackonis (2013), Olsson (2005), Sosa (1980, 1989), Swanton (1992), and Thagard (1993). Reflective equilibrium (and to that extent coherence) is also connected with theory underdetermination and has roots in Quine’s view of theory evaluation. For more on theory underdetermination and the Quinean roots of contemporary reflective equilibrium, see Bergstrom (1984), Boyd (1973), Earman (1993), Glymour (1971), Laudan and Leplin (1991), Quine (1960, 1969, 1975), and Stanford (2013). I will examine reflective equilibrium and coherence in detail in chapter 3.
6 I put “theory” in quotation marks because this probably doesn’t even qualify as a theory since it is not a system of thought, but is instead a mere list of claims.
7 For more on simplicity as a method of theory evaluation, see Baker (2013), Derkse (1993), Sober (1975 and 2015), Swinburne (1997), and Walsh (1979). Simplicity is also often examined in the particular context of scientific theory evaluation. For more on simplicity as it particularly relates to science, see Bunge (1963), Chandrasekhar (1987), Feuer (1957), Forster and Sober (1994), Hillman (1962), Kemeny (1953), and McAllister (1999). For more on explanatory virtues, including but not limited to simplicity
