The paper examines the nature of scientific progress through the lens of the history of modern cosmology (i.e. from Einstein’s, 1917 static universe to the present-day Standard (ΛCDM) model of cosmology). We distil three novel lessons, germane to the debate between the two main accounts of scientific progress (the noetic and the epistemic one, respectively). First, it’s difficult to sharply locate—to precisely pinpoint the locus of—the epistemic content of scientific knowledge. Cosmology displays stark epistemic holism: epistemic content and evidence are typically inextricably distributed over a wider “web of beliefs”. Secondly, cosmologists employ a variety of justificatory practices and modes of reasoning. More often than not, they fall short of the fastidious standards of traditional epistemology. Thirdly, cosmological claims typically defy easy and unambiguous characterisation in terms of truth. These three lessons are shown to pose grave challenges to the epistemic account of scientific progress (on which progress consists in the accumulation of knowledge). By contrast, the rivalling noetic account (which characterises progress in terms of improved understanding) can naturally accommodate those lessons.
