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In philosophical epistemology, there are two types of coherentism: the coherence theory of truth,[1] and the coherence theory of justification[2] (also known as epistemic coherentism).[3]
Coherent truth is divided between an anthropological approach, which applies only to localized networks ('true within a given sample of a population, given our understanding of the population'), and an approach that is judged on the basis of universals, such as categorical sets. The anthropological approach belongs more properly to the correspondence theory of truth, while the universal theories are a small development within analytic philosophy.
The coherentist theory of justification, which may be interpreted as relating to either theory of coherent truth, characterizes epistemic justification as a property of a belief only if that belief is a member of a coherent set. What distinguishes coherentism from other theories of justification is that the set is the primary bearer of justification.[4]
As an epistemological theory, coherentism opposes dogmatic foundationalism and also infinitism through its insistence on definitions. It also attempts to offer a solution to the regress argument that plagues correspondence theory. Brand Blanshard argues that where we seem to determine truth from a proposition's self-evidence, we are in fact using coherence as a criterion of truth to certify the proposition as true. For the certainty of the truth of a proposition like '2 + 2 = 4', one rather appeals "to the coherence of [one's] proposition with an enormous mass of others" whose truth must stand or fall with it.[5]
Coherentism is a view either about the structure and system of knowledge and truth, or else justified belief. The coherentist's thesis is normally formulated in terms of a denial of its contrary, such as dogmatic foundationalism, which lacks a proof-theoretical framework, or correspondence theory, which lacks universalism. Counterfactualism, through a vocabulary developed by David K. Lewis and his many worlds theory[6] although popular with philosophers, has had the effect of creating wide disbelief of universals amongst academics. Many difficulties lie in between hypothetical coherence and its effective actualization. Coherentism claims, at a minimum, that not all knowledge and justified belief rest ultimately on a foundation of noninferential knowledge or justified belief. To defend this view, they may argue that conjunctions (and) are more specific, and thus in some way more defensible, than disjunctions (or).
After responding to foundationalism, coherentists normally characterize their view positively by replacing the foundationalism metaphor of a building as a model for the structure of knowledge with different metaphors, such as the metaphor that models our knowledge on a ship at sea whose seaworthiness must be ensured by repairs to any part in need of it. This metaphor fulfills the purpose of explaining the problem of incoherence, which was first raised in mathematics. Coherentists typically hold that justification is solely a function of some relationship between beliefs, none of which are privileged beliefs in the way maintained by dogmatic foundationalists. In this way universal truths are in closer reach. Different varieties of coherentism are individuated by the specific relationship between a system of knowledge and justified belief, which can be interpreted in terms of predicate logic, or ideally, proof theory.[7]