Understanding Discordant Evidence in Science and Policy

This dissertation studies scientific evidence, a notion ubiquitous in science and in applying scientific results to policy. It focuses on the problem of discordant, or contradictory, evidence and its use in policy. The problem is one of uncertainty, and emerges when pieces of evidence produced by scientists point to contradictory conclusions. Which evidence should scientists prioritize, and who should policymakers listen to in these cases? Philosophers of science have worked on the notion of evidence from a variety of epistemic, historical and methodological perspectives. Looking at this literature is like gazing into a fractured mirror: the pieces are there, but the reflection they produce is imperfect and disunified. This dissertation develops a theory of evidence that shows how the fractured pieces hang together. It provides solutions to the problem of discordant evidence. By critically engaging with the extant literature on evidence, the dissertation articulates the specific epistemic and methodological questions related to discordant evidence and proposes solutions to them. By fostering a connection with scientific practice, the framework of evidence that the dissertation develops is relevant for philosophers, scientists and policymakers alike.