Fragmented justification

Abstract This article presents a fragmented account of justification. The account is motivated via an example from climate science where, within the IPCC assessment report for climate change, an overall inconsistent set of justified beliefs seems to be asserted. The main reason why this happens will be the extreme uncertainty involved in learning about complex systems such as the climate. The article explains how the toolkit of traditional epistemology is limited in and not suited for dealing with situations like this, and argues that fragmentation is a more appropriate strategy than existing approaches to deal with (seemingly rational) inconsistent doxastic states. After presenting the example, the article gives a formalisation of this example. The upshot of this formalisation is that justifications are represented via non-monotonic fragment-indexed justification relations that hold between propositions that need justification, and evidence. The article explains why fragmentation is rationally warranted here, and develops an explicit set of precautionary norms that should guide the fragmentation process. It, furthermore, argues that the account of fragmented justification developed here is compatible with fragmented belief, and how this account of fragmented justification can serve as a novel argument for the rationality of fragmented belief accounts developed in the literature. And lastly, the article explains how sometimes, even though fragmentation might be epistemically rational, de-fragmentation will become necessary in light of practical rationality. It shows how de-fragmentation can work for epistemically rational fragmented agents, which is a novel discussion within the literature on fragmentation.