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.
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.
As an illustration of the principle, if people lived in a virtual reality universe, they could see birds in the trees that aren't really there.
The people may or may not know that the bird and the tree are there, but in either case there is a coherence between the virtual world and the real one, expressed in terms of true beliefs within available experience.
It therefore falls into a group of theories that are sometimes deemed excessively generalistic, what Gábor Forrai calls 'blob realism'.
[8] Perhaps the best-known objection to a coherence theory of truth is Bertrand Russell's argument concerning contradiction.
Coherence must thus rely on a theory that is either non-contradictory or accepts some limited degree of incoherence, such as relativism or paradox.
Additional necessary criteria for coherence may include universalism or absoluteness, suggesting that the theory remains anthropological or incoherent when it does not use the concept of infinity.
A coherentist might argue that this scenario applies regardless of the theories being considered, and so, that coherentism must be the preferred truth-theoretical framework in avoiding relativism.
In modern philosophy, the coherence theory of truth was defended by Baruch Spinoza,[1] Immanuel Kant,[1] Johann Gottlieb Fichte,[1] Karl Wilhelm Friedrich Schlegel,[9] and Georg Wilhelm Friedrich Hegel[1] and Harold Henry Joachim (who is credited with the definitive formulation of the theory).
[11] In late modern philosophy, epistemic coherentist views were held by Schlegel[12] and Hegel,[13] but the definitive formulation of the coherence theory of justification was provided by F. H. Bradley in his book The Principles of Logic (1883).
[14] In contemporary philosophy, epistemologists who have significantly contributed to epistemic coherentism include: A. C. Ewing, Brand Blanshard, C. I. Lewis, Nicholas Rescher, Laurence BonJour, Keith Lehrer, and Paul Thagard.
[15] Both coherence and foundationalist theories of justification attempt to answer the regress argument, a fundamental problem in epistemology that goes as follows.
This would serve the typical purpose of circumventing the reliance on a regression, but might be considered a form of logical foundationalism.
But otherwise, it must be assumed that a loop begs the question, meaning that it does not provide sufficient logic to constitute proof.
For instance, rationalists such as Descartes and Spinoza developed axiomatic systems that relied on statements that were taken to be self-evident: "I think therefore I am" is the most famous example.
The Coherentist analytic project then involves a process of justifying what is meant by adequate criteria for non-dogmatic truth.
Catherine Elgin has expressed the same point differently, arguing that beliefs must be "mutually consistent, cotenable, and supportive.
At this point, Coherence could be faulted for adopting its own variation of dogmatic foundationalism by arbitrarily selecting truth values.
A second objection also emerges, the finite problem: that arbitrary, ad hoc relativism could reduce statements of relatively insignificant value to non-entities during the process of establishing universalism or absoluteness.
Coherentists generally solve this by adopting a metaphysical condition of universalism, sometimes leading to materialism, or by arguing that relativism is trivial.
One strategy is to argue that no set of beliefs held by an agent would remain coherent over time if it was isolated from the external world in this way.