Inference to the Source: The Case of Observing a Binary Black Hole Merger

The philosophical literature is replete with the discussion of theory-laden observation and circularity with regard to the evidential role of observation in testing and confirming theories. However, only a few philosophers have situated this discussion within the process of observation itself, that is, theory ladenness and circularity with respect to inference to the source. It has been argued that in order to infer the source reliably, the theory of the source should not be involved in the process of observation [1, 2] or, if it is, there should be an independent empirical access [3].

A number of scientists and philosophers of science have raised concerns about the epistemic aspects of observing binary black hole mergers. Specifically, concerns have been raised about the theory/model ladenness of binary black hole observation and its evidential role in testing general relativity in this extreme gravitational regime [4], as well as the alleged circularity of the observation [5]. Given that the observation of binary black hole merger does not fulfill any of the normative conditions for the inference to the source suggested by the philosophical accounts, how can it be accounted for?

In this paper, I argue that concerns about circularity in binary black hole observation is a consequence of the H-D method, and that the epistemic threat, if any, comes not from the theory-laden process, but from the underdetermination of the source by the collected data, since the data could be explained by proposing inconsistent sources for the gravitational waves. To reliably infer the source is to overcome this underdetermination. I will further argue that a bidirectional version of inference to the only explanation captures the situation well and mitigates concerns about the inaccuracy of the models with respect to GR. However, to provide a full epistemic justification for the observation regarding the viability of GR as a background theoretical framework and its accurate description of the source system, one needs a broader conception of evidence to overcome the underdetermination. To this end, I will argue that the integration of meta-empirical assessments developed by Dawid [6] into the inference to the only explanation is a promising strategy as a justifiable extension of the concept of evidence.

References:
[1] Ian Hacking. Representing and Intervening: Introductory Topics in the Philosophy of Natural Science. New York: Cambridge University Press, 1983.

[2] Peter Kosso. “Dimensions of Observability”. In: British Journal for the Philosophy of Science 39.4 (1988), pp. 449–467.

[3] Allan Franklin. Selectivity and Discord: Two Problems of Experiment. University of Pittsburgh Press, 2002.

[4] Nicolas Yunes and Frans Pretorius. “Fundamental theoretical bias in gravitational wave astrophysics and the parametrized post-Einsteinian framework”. In: Phys. Rev. D 80 (12 Dec. 2009), p. 122003.

[6] Jamee Elder. “Black Hole Coalescence: Observation and Model Validation”. In: Working Toward Solutions in Fluid Dynamics and Astrophysics: What the Equations Don?t Say. Ed. by Lydia Patton and Erik Curiel. Springer Verlag, 2023, pp. 79–104.

[6] Richard Dawid. “Delimiting the Unconceived”. In: Foundations of Physics 48.5 (2018), pp. 492–506.