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Olsson, Erik J. Against Coherence. Truth, Probability, and Justification.

OLSSON, Erik J. Against Coherence. Truth, Probability, and Justification. Oxford: Oxford University Press, 2005. xiii + 232 pp. Cloth, $37.00--Against Coherence explores the relationship between coherence and truth. Olsson critically assesses the claims of important scholarly accounts of this relationship with a strong emphasis on C. I. Lewis's A Theory of Knowledge and Valuation (1946), Laurence BonJour's The Structure of Empirical Knowledge (1985), the work of Peter Klein and Ted A. Warfield, L. Jonathan Cohen's The Probable and the Provable (1977) and C. A. J. Coady's Testimony: A Philosophical Study (1992). He demonstrates that there cannot be truth based on coherence. This must not lead to radical skepticism as he presents an alternative based on C. S. Peirce's pragmatism.

Olsson analyzes C. I. Lewis's claims and establishes his congruence-truth relationship binges on the credibility of witnesses. Without credibility, congruence does not imply truth. Lewis considers that memory contains the necessary minimum condition for credibility that allows the distinction between facts and fictions. Olsson criticizes this assumption by referring to the delusional mind.

He also challenges Lewis's congruence-truth relationship even under the assumption of the credibility of memory. Lewis cannot establish a degree of credibility for memory which makes it very problematic to establish probability based on congruence.

BonJour uses beliefs to establish coherence. Olsson is critical of the claim that coherence based on independent beliefs (even this independence is a questionable assumption due to outer influences on beliefs) without assuming the credibility of those beliefs can lead to a truth claim. Olsson uses liars as proof that independent testimonies also need to be credible to make coherence meaningful.

Coady sees credibility in the trust we have in the testimony of others. He develops this out of his criticism of Hume who establishes trust based on the reliability of experiences. Coady sees in this argument a fatal ambiguity because individuals rely on the testimony of others for common experiences (most convictions cannot be verified by individual experiences). Coady derives from reports conveying meaning that there must be a connection between reality and report. Considering that no degree of reliability can be established, Olsson sees Coady's argument to suffer from the same weakness as Lewis's argument with regards to the credibility of memory. The impossibility to infer reliability from cohesion of reports leads Olsson to state that Coady is caught in a similar ambiguity as Hume.

Olsson concludes Part I ("Does Coherence Imply Truth") with the finding that coherence theory of truth hinges on independence and initial testimonial credibility and that coherence theory is thus not able to counter radical skepticism.

Part II explores the question whether content coherence of testimonies can imply a higher likelihood of truth. Olsson will answer this question in the negative by arguing that it is most unlikely that coherence can infer even likelihood of truth due to the complexity of the assumptions that need to be met for such a claim. One issue is the importance of prior probability of content that cannot be derived from coherence. Another issue is the independence of beliefs. "Cognitively spontaneous beliefs" (p. 102) are hard to define. Also, the probability of reliability is an important factor (Klein and Warfield). In assessing Cohen's claim of the dependence of the posterior on the prior, Olsson misses the need to consider the prior probability of reliability. Olsson thus establishes his Impossibility Theorem saying that "There are no informative coherence measures that are truth conducive ceteris paribus in a basic Lewis scenario (given independence and individual credibility)" (p. 135). This does not question higher probability in cases of independence and individual credibility. It only challenges the truth claim of coherence in cases where there is no knowledge of reliability.

In Part III, Olsson investigates whether this verdict might change using the Principle of Indifference as advocated by Bovens, Fitelson, Hartmann, and Snyder. This assumes degrees of credibility based on prior probability. Olsson does not agree that degrees of individual credibility can be thus assigned.

Olsson explores other coherence theories. He sees Nicholas Rescher investigating plausibility and not coherence; Donald Davidson focusing on beliefs and meaning; Keith Lehrer's "justification game" (p. 160) lacking the mutual support of testimonies necessary for coherence considerations; Paul Thagard's emphasizing explanations over probability not being able to overcome the problems created by the need of independence and credibility for a truth claim.

In Part IV, "Skepticism and Incoherence," Olsson dismisses William James's wager argument to trust our beliefs against radical skepticism. He develops Peirce's argument, though, that we should not follow the skeptic's assumption not to know that we are not deceived. This is explained by the starting point of all inquiries that is our doxastic system that cannot be replaced by a skeptic neutral perspective leading to hypotheses that are useless for life's need to find guidance. This is contrasted with contextualism though Olsson sees the familiarity between contextualism and pragmatism. Olsson concludes that coherence cannot be truth inducing but that it still can serve to validate our beliefs.--Erich P. Schellhammer, Royal Roads University.
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Author:Schellhammer, Erich P.
Publication:The Review of Metaphysics
Article Type:Book review
Date:Dec 1, 2007
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