In this Special Issue, we explore the rise of non-empirical physics from a historical perspective. This exercise is meant, furthermore, as an attempt to open new pathways in contemporary history and philosophy of physics. We use this introduction to provide the theoretical background necessary to flesh out this program and to appreciate the manner in which the different articles in the collection substantiate it. To do this, we proceed in the following manner. First, we briefly lay out the development of contemporary philosophy of physics, and the manner in which the range of topics covered in the specialized literature expanded over the past few decades. After that, we chronicle the advent of non-empirical physics during the second half of the twentieth century, and we introduce the philosophical debates triggered by this development. These debates, as we show, did introduce new topics of discussion in the literature. However, these discussions did not arise as a deliberate attempt to add new ideas to the philosophy of physics repertoire. Instead, they emerged as a natural consequence of the historical development of physics itself. Taking this observation as our starting point, we argue that engaging with the controversies around non-empirical physics, and with the historical circumstances behind their appearance, provides a more fruitful, more historically grounded approach towards updating the canon of philosophy of physics. We then single out some areas in which further historical work is particularly promising, and we highlight the contributions made by each one of our authors. We conclude by inviting others to join the philosophical program sketched here, and to add their own insights to the ones contained in this Special Issue.

Physics and mentality are most often understood to be paradigmatically separate fields of inquiry. The foundational debate has a long history of attempts, however, to introduce aspects of mentality into physical analysis. In the context of Everettian quantum mechanics considerations of this kind play out in a different way than in collapse theories. This paper reviews some of those thoughts.

We provide a philosophical reconstruction and analysis of the debate on the scientific status of cosmic inflation that has played out in recent years. In a series of critical papers, Ijjas, Steinhardt, and Loeb have questioned the scientificality of current views on cosmic inflation. Proponents of cosmic inflation, such as Guth and Linde, have in turn defended the scientific credentials of their approach. We argue that, while this defense, narrowly construed, is successful against Ijjas, Steinhardt, and Loeb, the latters’ reasoning does point to a significant epistemic issue that arises with respect to inflationary theory. We claim that a broadening of the concept of theory assessment to include meta-empirical considerations is needed to address that issue in an adequate way.

We discuss the proposal by Sebens and Carroll to derive the Born rule in Everettian quantum mechanics from a principle they call ‘ESP-QM’. We argue that the proposal fails: ESP-QM is not, as Sebens and Carroll argue, a ‘less general version’ of an independently plausible principle, ESP, and can only be motivated by the empirical success of quantum mechanics, including use of the Born rule. Therefore, ESP-QM cannot have the status of a meta-theoretical principle of reasoning and provides no viable basis for deriving the Born rule.

I respond to three points of criticism that have been raised against the concept of meta-empirical confirmation. I argue that meta-empirical confirmation can be set up in a coherent way and is sufficiently discriminating for rendering it a non-trivial indicator of a theory's viability. Moreover, I argue that acknowledging the significance of meta-empirical confirmation provides an argument for the pursuit of alternative research programs rather than for their suppression.

While ΛCDM has emerged as the standard model of cosmology, a small group of physicists defends modified newtonian dynamics (MOND) as an alternative view on cosmology. Exponents of MOND have employed a broad, at times explicitly philosophical, conceptual perspective in arguing their case. This paper offers reasons why that MONDian defense has been ineffective. First, we argue that the defense is ineffective according to Popperian or Lakatosian views–ostensibly the preferred philosophical views on theory assessment of proponents of MOND. Second, we argue that the defense of MOND can instead best be reconstructed as an instance of meta-empirical theory assessment. The formal employment of meta-empirical assessment by MONDians is unconvincing, however, because it lacks a sufficient epistemic foundation. Specifically, the MONDian No Alternatives Argument relies on falsifiability or explanation conditions that lack epistemic relevance, while the argument from Unexpected Explanatory Success fails since there is a known alternative to MOND. In the last part of the paper, we draw some lessons for applications of meta-empirical assessment more generally.

In a recent article, Menon has argued that the no alternatives argument can only be significantif the priors for numbers of alternatives are tuned in an implausible way (gerrymandered, as he calls it). In this article, I demonstrate that priors needed for making a no alternatives argument significant are in line with what can be plausibly assumed in a successful research field.

The universal acceptance of atomism in physics and chemistry in the early 20th century went along with an altered view on the epistemic status of microphysical conjectures. Contrary to the prevalent understanding during the 19th century, on the new view unobservable objects could be 'discovered'. It is argued in the present paper that this shift can be connected to the implicit integration of elements of meta-empirical theory assessment into the concept of theory confirmation.

Moritz Schlick’s interpretation of the causality principle is based on his understanding of quantum mechanics and on his conviction that quantum mechanics strongly supports an empiricist reading of causation in his sense. The present chapter compares the empiricist position held by Schlick with Bas van Fraassen’s more recent conception of constructive empiricism. It is pointed out that the development of philosophy of science from Schlick’s understanding of logical empiricism to constructive empiricism reflects a difference between the understanding of quantum mechanics endorsed by Schlick and the understanding that had been established by the time of van Fraassen’s writing.