 One aspect of underdetermination (emphasized by Stanford 2006) is of more direct relevance to scientific debates: current theories may be indistinguishable, within a restricted domain, from a successor theory, even though the successor theory makes different predictions for other domains. This raises the question of how far we can rely on extrapolating a theory to a new domain. For example, despite its success in describing objects moving with low relative velocities in a weak gravitational field, where it is nearly indistinguishable from general relativity, Newtonian gravity does not apply to other regimes. How far, then, can we rely on a theory to extend our reach? The obstacles to making such reliable inferences reflect the specific details of particular domains of inquiry. Below we will focus on the obstacles to answering theoretical questions in cosmology due to the structure of the universe and our limited access to phenomena.