What Is Coherentism?

Direct Answer

Coherentism is an answer to a fundamental question in epistemology: what makes a belief justified? Where foundationalism says that some beliefs are basic — justified without relying on other beliefs — and that all other beliefs derive their justification from these foundations, coherentism denies that there are any basic beliefs. Instead, it holds that justification is holistic: a belief is justified when it coheres with the total system of one's beliefs.

The standard metaphor for coherentism is a web. Imagine your beliefs as nodes in a network, connected by inferential threads. No single node is self-supporting; each draws its stability from its connections to the others. A belief is justified not because it sits at the bottom of a structure but because it is woven into the fabric of your belief system in the right way — it is consistent with your other beliefs, it is supported by them, and it in turn helps support them. The strength of the web depends not on any single thread but on the density and quality of the connections among all the threads.

What does it mean for a belief to "cohere" with a system? Philosophers have identified several components. First, there is logical consistency: a belief that contradicts other beliefs in the system fails to cohere. Second, there is inferential connection: a belief should be related to other beliefs by relations of explanation, implication, or probabilistic support. Third, there is explanatory integration: a coherent system doesn't just avoid contradiction but provides a unified explanation of the phenomena it covers. The more a belief contributes to the explanatory power and unity of the system, the more it coheres.

Coherentism is motivated by the same regress argument that motivates foundationalism, but it takes a different turn. The regress argument notes that if every belief needs to be justified by another belief, we face either an infinite regress, circularity, or a stopping point. Foundationalists opt for the stopping point — basic beliefs. Coherentists accept a version of circularity, but they argue that it is not the vicious circularity of "A is justified because B, and B is justified because A." Instead, it is a holistic mutual support: the system as a whole is justified by its coherence, and individual beliefs are justified by their place within the coherent whole.

Historical Context

The Stanford Encyclopedia of Philosophy notes that while coherentism as a systematic epistemological theory is primarily a twentieth-century development, its roots can be traced to earlier philosophical traditions. The British idealist F.H. Bradley, in Appearance and Reality (1893), argued that reality is a single, coherent system of experience and that truth consists in coherence with this system. This idealist version of coherentism influenced later thinkers, though it was developed in a metaphysical rather than a purely epistemological direction.

The modern coherentist tradition in epistemology was launched by W.V.O. Quine's influential essay "Two Dogmas of Empiricism" (1951). Quine argued that our beliefs form a "web of belief" that faces the tribunal of experience as a whole, not individually. No belief is immune to revision — not even the truths of logic and mathematics — and the effect of recalcitrant experience is redistributed across the web according to pragmatic considerations. Quine's holism undermined the foundationalist picture by denying that there is a sharp distinction between beliefs that are directly confirmed by experience and beliefs that are confirmed indirectly. All confirmation is holistic, on Quine's view, and the idea of basic, self-justifying beliefs is an illusion.

The most detailed defense of coherentism as a theory of epistemic justification was provided by Laurence BonJour in The Structure of Empirical Knowledge (1985). BonJour argued that foundationalism fails because it cannot provide a satisfactory account of how basic beliefs justify non-basic beliefs, and that coherentism offers a superior alternative. On BonJour's view, a belief is justified if and only if it is a member of a system of beliefs that is coherent and that includes beliefs about the cognitive processes by which the system is maintained. BonJour's version of coherentism is demanding: it requires not just that one's beliefs be mutually consistent but that one have meta-beliefs about the reliability of one's cognitive processes.

Other important contributors to the coherentist tradition include Donald Davidson, who argued that coherence is the only possible measure of truth and justification because there is no neutral standpoint from which to compare beliefs with bare reality. Gilbert Harman has defended a form of coherentism based on the idea that justification proceeds by "inference to the best explanation," with beliefs being justified by their role in the best explanatory system available.

Philosophical Perspectives

Coherentism faces two major objections that have shaped the debate. The first is the isolation problem (sometimes called the input problem): a perfectly coherent system of beliefs might be entirely disconnected from reality. Imagine a person whose beliefs form an internally consistent, mutually supportive, explanatorily powerful system but whose beliefs are all false — perhaps they are the victim of a systematic deception, or perhaps they inhabit a carefully constructed virtual reality. Their beliefs cohere perfectly, but they do not constitute knowledge. If coherentism says that coherence alone is sufficient for justification, then it seems to imply that this deluded person is justified in their beliefs, which is deeply counterintuitive.

Coherentists have responded to this objection in several ways. Some, like BonJour, argue that the coherence of a system must include beliefs about the reliability of the cognitive processes that produce it. A system that includes the belief "my perceptual faculties are generally reliable" is more coherent than one that does not, because it can explain why its beliefs about the external world are as they are. But critics argue that this just pushes the problem back: a perfectly deluded person might also have beliefs about the reliability of their faculties, and those beliefs would be just as deluded.

Other coherentists accept that coherence alone may not be sufficient for knowledge and supplement their view with a requirement that the belief system be appropriately caused by or responsive to the external world. This "weak coherentism" or "moderate coherentism" holds that coherence is the structure of justification but that some external constraint — like causal connection to the world — is needed for knowledge. The Stanford Encyclopedia of Philosophy notes that this hybrid approach blurs the line between coherentism and foundationalism, since the external constraint functions something like a foundational element.

The second major objection is the plurality problem: there can be multiple, mutually incompatible but individually coherent systems of beliefs. If two people hold different belief systems, each internally coherent but inconsistent with the other, coherentism seems unable to say which (if either) is justified. The foundationalist can appeal to basic beliefs as a common standard, but the coherentist has no neutral ground on which to adjudicate. This objection is particularly pressing in cases of deep disagreement — between different scientific paradigms, different moral frameworks, or different cultural worldviews.

Coherentists respond that not all coherent systems are equally good. Coherence is a matter of degree, not an all-or-nothing property. A system that is more comprehensive, more unified, more explanatorily powerful is more coherent than one that is less so. When two systems conflict, we can compare them along these dimensions. Critics argue that this response is too vague: the criteria of coherence are not precise enough to settle real disagreements, and different parties may reasonably disagree about which system is more coherent.

Despite these challenges, coherentism has attracted defenders who find the foundationalist alternative even more problematic. The regress argument, they argue, shows that foundationalism is untenable because no belief is truly basic — every belief can be questioned, and the supposedly basic beliefs always turn out to rest on assumptions that are themselves beliefs. The coherentist's holistic picture, they contend, better captures the actual practice of justification: when we justify our beliefs, we do not appeal to foundations but to the way our beliefs fit together and explain our experience.

Modern Reflection

The debate between coherentism and foundationalism has evolved in contemporary epistemology, with many philosophers adopting positions that draw on both traditions. One important development is the rise of "weak foundationalism" or "moderate foundationalism," which accepts that some beliefs have a degree of non-inferential justification but denies that this justification is sufficient for knowledge. On this view, basic beliefs provide input to the system, but the system's overall coherence is what converts that input into full-blown justification. This hybrid approach attempts to capture the insights of both foundationalism (the need for some connection to experience) and coherentism (the holistic nature of justification).

Another development is the influence of Bayesian epistemology, which models belief revision in terms of probabilistic coherence. On the Bayesian picture, a rational agent's beliefs should form a probability distribution that is internally consistent (satisfying the axioms of probability) and that is updated by conditionalization on new evidence. This is a form of coherentism — justification depends on the overall structure of one's probabilistic beliefs — but it incorporates a role for evidence that addresses the isolation problem. The Bayesian framework has become increasingly influential in formal epistemology, though it raises its own questions about the choice of prior probabilities and the interpretation of probability.

The coherentist picture also resonates with developments in the philosophy of science. Thomas Kuhn's account of scientific paradigms, which emphasizes the role of conceptual frameworks in shaping what scientists observe and believe, has coherentist implications. Within a paradigm, beliefs are mutually supporting and justified by their role in the paradigm's research program. Paradigm shifts involve a reorganization of the entire belief system, not just the addition of new data. This picture is closer to coherentism than to foundationalism, though Kuhn himself did not endorse coherentism as a general epistemological position.

In contemporary ethics and political philosophy, coherentist ideas appear in the method of reflective equilibrium, developed by John Rawls. In reflective equilibrium, one adjusts one's principles and one's particular judgments until they cohere into a unified system. This method is coherentist in structure: neither the principles nor the judgments are basic; each is justified by its fit with the others. The wide acceptance of reflective equilibrium as a method in ethics suggests that coherentist thinking has applications beyond theoretical epistemology.

Related Thinkers

Aristotle discussed the structure of knowledge in ways that have been read as both foundationalist and coherentist, depending on the interpreter. In the modern era, W.V.O. Quine's holism was a major catalyst for coherentist thinking, particularly his "web of belief" metaphor. Laurence BonJour provided the most systematic defense of coherentism in The Structure of Empirical Knowledge (1985), though he later abandoned the view. Donald Davidson argued that coherence is the measure of truth and justification, while Gilbert Harman defended coherentism through inference to the best explanation. On the critical side, foundationalists like William Alston and Richard Foley have pressed objections that continue to shape the debate.

Related Quotes

Quine's image of the "web of belief" has become one of the most famous metaphors in epistemology. In "Two Dogmas of Empiricism," he wrote: "The totality of our so-called knowledge or beliefs, from the most casual matters of geography and history to the profoundest laws of atomic physics or even of pure mathematics and logic, is a man-made fabric which impinges on experience only along the edges." This passage captures the coherentist intuition that beliefs form an interconnected system, with experience constraining the system as a whole rather than providing secure foundations for individual beliefs.

Further Learning

1. Stanford Encyclopedia of Philosophy, Coherentist Theories of Epistemic Justification.
2. Laurence BonJour, The Structure of Empirical Knowledge (Harvard University Press, 1985).
3. W.V.O. Quine, "Two Dogmas of Empiricism," The Philosophical Review 60 (1951): 20-43.
4. Donald Davidson, "A Coherence Theory of Truth and Knowledge," in Truth and Interpretation (Blackwell, 1986).
5. Keith Lehrer, Theory of Knowledge (Westview Press, 2nd ed., 2000).
6. Susan Haack, Evidence and Inquiry (Blackwell, 1993).

To explore related concepts, consider reading about epistemology, foundationalism, and the nature of truth.