Abstract: Sceptics have often cast doubt on the legitimacy of claims to the effect that our best scientific theories are true. One ground for such scepticism is the fact that our theories advert to the existence and nature of unobservable entities and features of the world. Another ground for such scepticism is the fact that our theories rest upon our idealization of the world in their descriptions and explanations. A third ground for scepticism is the claim that all of our theories are but transient. If we expect even our best theories to ultimately be replaced, how can we think of them as truly describing the world? Each kind of sceptical argument plays a role within the scientific project of theory construction and evaluation itself. But there are clear and important differences between the kinds of internal role such arguments play within science and the way that they function in the more abstract philosophical context.

Keywords: idealization, philosophy of science, scientific explanation, scientific theory, Lawrence Sklar, scepticism, transience, unobservables