One intuitively wouldn’t want to have a set of incoherent beliefs. Preferring incoherence is to be frowned upon, for one belief in this set must be false. Any sort of epistemology should then strive for some kind of coherence and mutual support, and if incoherence is found, of finding a way to determine which member of the set is false and which is true.
There are two kinds of coherentism I’m thinking of: the first kind is sort of a nebulous coherentism, that it is better to prefer a set of beliefs that support one another over a set of incoherent beliefs. I would then call myself a ‘weak’ coherentist in a sense, as would most modern epistemologists, but we strive not just for the coherence of our beliefs as indicating its truth, but for the truth of all of our beliefs.
The second kind of coherentism I will call ‘strict coherentism.’ It sees no recourse necessary to any sort of a posteriori examination. This gambit is played, I think, in order to circumnavigate a serious problem for most justificationists: we may be justified in preferring a coherent system over an incoherent system.
Alice’s memory is wiped in a freak accident. She is recovering in a hospital room when a mad scientist abducts her and implants the following ideas in her head so that she holds them a priori:
p: ‘Barney the dinosaur exists’
q: ‘Barny talks’
r: ‘All dinosaurs talk’
Each member of the set is epistemically supported by the other members. ‘Barney the dinosaur’ can be replaced by any other nonexistent entity. ‘Talks’ can be replaced by any other property.
Thus, there are an infinite number of coherent systems that consists of false statements. If someone wishes to have a true coherent system, it appears that they better adopt some beliefs acquired through a posteriori examination. While we may give more weight to coherent systems over incoherent systems, that does not amount to much. We still need to determine which systems are true.
Quine’s holism matches with strict coherentist’s lack of interest in a posteriori examination. It is better, so Quine thinks, that the whole be maintained rather than to revise basic propositions. It is true that, if we so wish, we can maintain the whole come what may at the expense of the part. All crucial tests are theory-laden, so no ‘refutation’ is ever final. They remain ever-conjectural. We can make the choice to sacrifice nearly any part of the system to retain coherence, but often we will put to death a part that may be true, such as an observation report about the consequences of a crucial test, to keep a false theory protected from criticism.
Yet, this culling of the undesirables, while at times leading to true outcomes, may also lead to a willingness, as Quine admits, to revising all sorts of things, including the laws of logic from destroying an entire system.
I should make it clear that as a supporter of Bartley’s comprehensively critical rationalism, I admit that this revision may take place. I also admit that my beliefs may be incoherent. Yet, this admission does not constitute a criticism: I require more. We very well might, some time in the future, have to change what we take to be the very laws of logic. However, this would occur only under intense criticism, not out of a conventionalist stratagem to retain coherence at the expense of an observation report.