Jared Hanson-Park

This paper argues that realism is best defended across the sciences by appealing to the notion of detection properties. While much of the realism debate has focused on physics, where object-oriented accounts of realism have been prominent, the notion of unobservable objects does not apply as readily in other scientific fields. I show that detection properties—causal properties that scientists have managed to detect through various experimental means—provide a strong basis for realism in various fields within both the physical and life sciences. I take a comparative approach, and I examine how knowledge of detection properties can be gained across diverse scientific disciplines with varying subject matter and methodologies. In this way, this paper demonstrates that a more robust and universally applicable articulation of realism can be achieved by appealing to detection properties as a central feature of realism in each field. This approach highlights the importance of recognizing the epistemically relevant differences between scientific fields for a nuanced defense of realism.

Epistemic Structural Realism (ESR), the view that structure is all we can know about the unobservable world, has been criticized for lacking sufficient metaphysical depth to qualify as a genuine form of realism. This paper defends a refined version of ESR – which I call agnostic ESR – that avoids these objections by committing to knowledge of detectable, concrete structures while maintaining agnosticism about the existence of objects with intrinsic properties. I respond to prominent criticisms, including Newman’s objection, concerns about ESR’s metaphysical clarity, and potential collapse into other views, by showing that agnostic ESR can provide a rigorous account of structural knowledge grounded in empirical science that cannot be defended by advocates of other realist positions. I argue that agnostic ESR is metaphysically robust to deserve the realist label.

Structural realists claim that structure is preserved across instances of radical theory change, and that this preservation provides an argument in favor of realism about structure. In this paper, I use the shift from Newtonian gravity to Einstein’s general relativity as a case study for structural preservation, and I demonstrate that two prominent views of structural preservation fail to provide a solid basis for realism about structure. The case study demonstrates that (i) structural realists must be epistemically precise about the concrete structure that is being preserved, and (ii) they must provide a metaphysical account of how structure is preserved through re-interpretation in light of a new theory. Regarding (i), I describe a means of epistemic access to the unobservable that I call “thick detection” of structure, which isolates the structure that will be preserved. Regarding (ii), I argue that thickly detectable structure is preserved across theory change through a process of extracting the old structure from the new structure, much like what has been done with geometrized versions of Newtonian gravity. With these two responses in hand, the structural realist can adequately account for the preservation of structure and can provide a strong argument in favor of structural realism.

Among scientific realists and anti-realists, there is a well-known, perennial dispute about the reality and knowability of unobservable objects. This dispute is also present among structural realists, who all agree that science gives us genuine knowledge of structure at the unobservable level (however that structure may be understood). Ontic structural realists reduce or eliminate the ontological role of objects, while epistemic structural realists argue that objects do or might exist but are unknowable. In part because ontic structural realism has some evidence from quantum mechanics and the consequent underdetermination of the metaphysics of objects in its favor, the majority of contemporary structural realists adopt that view. In contrast, I argue that epistemic structural realism is a highly compelling view, particularly in the form that remains agnostic about unobservable objects. This view can remain consistent with the empirical data from quantum mechanics, can give a satisfactory account of the metaphysics of structure, and can distinguish itself from other extant versions of realism. I provide two arguments in favor of agnosticism about objects, the first of which argues that suspending belief is consistent with the impetus of naturalized metaphysics, and the second of which argues that agnosticism about objects is a rational response to reflection on the limits and aims of science. Thus, I show that agnostic epistemic structural realism is a defensible and compelling view in the philosophy of science that demands more attention in the literature.