Laws, Initial Conditions and Physical Modality: Lessons from Cosmology

Abstract Certain considerations from cosmology (Ellis, in: arXiv preprint, 2006. arXiv:astro-ph/0602280 ; Stud Hist Philos Mod Phys 46:5–23, 2014) and other areas of physics (Sklar, in: PSA Proceedings of the biennial meeting of the philosophy of science association, pp. 551–564, 1990; Frisch, in: Philos Sci 71:696–706, 2004) pose challenges to the traditional distinction between laws and initial conditions, indicating the need for a more nuanced understanding of physical modality. A solution to these challenges is provided by presenting a conceptual framework according to which laws and fundamental lawlike assumptions within a theory’s nomic structure determine what is physically necessary and what is physically contingent from a physical theory’s point of view. Initial conditions are defined within this framework in terms of the possible configurations of a physical system allowed by the laws and other lawlike assumptions of a theory. The proposed deflationary framework of physical modality offers an alternative way of understanding the distinction between laws and initial conditions and allows the question of the modal status of the initial conditions of the Universe to be asked in a meaningful way.