"My beliefs could form a coherent set even if none of them is true." This statement implies a "somewhat realist" conception of truth -- a concept of truth that is independent of our own beliefs, however coherent they may be. (Note, however, that this "somewhat realist" concept of truth is consistent with some versions of an "anti-realist" conception of truth -- as I will elaborate below.) Given this basic premise, there are then two related but alternative ways of understanding the argument. One way is to see the argument as raising the issue of just how the notion of "coherence" results in our beliefs tracking the truth. On this understanding, the argument is suggesting that the coherence account of knowledge does not in fact track the truth. The other related way of understanding the argument is to consider the sceptical challenge that despite how things seem, they may in fact be radically different -- the Brain-in-a-Vat or "Matrix" hypothesis. On this understanding, the argument is suggesting that the coherence of a set of beliefs provides no defence against the sceptic's offering of "outlandish" alternatives. I shall consider first the question of whether the coherence account of knowledge can track the truth, assuming that things are in fact quite similar to how they seem. I will then address whether the coherence account of knowledge can deal with the sceptical challenge that things may in fact not be at all as they seem.
First, some background. The coherence
account of knowledge is a member of the family of "Justified-True-Belief" theories of knowledge. The traditional justified-true-belief theory maintains
S knows that P iff (1) P is true; and
(2) S believes that P; and
(3) S's belief that P is justified.
Most theories of knowledge are termed "internalist" because their concept of justification is based solely on things that are directly available to the knower. Internalist theories of knowledge and justification focus on the way we employ reasons to support conclusions from the evidence. When you list all the reasons you believe justifies your belief that P, what you are listing is other beliefs along with the associated second-order beliefs that the supporting evidence actually does imply P, or make P more probable.
However, if your knowledge is justified on the basis of other
beliefs, and those are in turn justified based on further beliefs, it is easy to
see that an infinite regress quickly develops. This form of sceptical challenge
is known as Agrippan (or Ancient Greek) Scepticism after the Five Modes of
Agrippa identified by Sextus Empiricus. The argument is that when challenged to
provide the reasons that justify any particular belief, you have only one of
1) Keep providing some new supporting reason -- i.e. embark on an infinite regress of reasons; or
2) At some point give up, and fall back on some basic dogmatic (and hence unjustified) assumption; or
3) At some point, repeat yourself -- i.e. reason in a circle.
The Agrippan Sceptic argues that none of these three alternatives is acceptable as a proper justification for your beliefs. Therefore, none of your beliefs are justified. Hence knowledge (conceived as justified true belief) is impossible to attain.
The Coherentist theory of knowledge
responds to the Agrippan sceptic by adopting the premise that beliefs can be
mutually supporting. Coherentism argues that reasoning in a circle does not
have to be circular reasoning. Unlike foundationalism, coherentism's
traditional competition, the coherence concept of justification is holistic
rather than linear or hierarchical. The coherence account of knowledge
S knows that P iff (a) P is true; and
(b) S believes that P; and
(c) S's belief that P coheres with the rest of S's belief-set.
A belief is appropriately justified, and qualifies as knowledge, if and only if it "coheres" with the rest of one's belief-set. However, it is not at all obvious that the coherence of a set of beliefs should or even could track reality. So the question is - does the coherence of a set of beliefs render those belief more likely to be true than not? To explore that question, we need to understand just what it means for a set of beliefs to "cohere."
Coherence theorists generally describe the coherence involved as "explanatory" coherence: A belief system is more coherent the more beliefs it incorporates into the network, the greater the range of beliefs it records, explains, and allows us to anticipate. Recognizing which beliefs are relevant and constructing theories to explain them are two aspects of a single process. The goal is to make our beliefs as coherent (ie explanatory) as we can. On this basis, a belief-system is more coherent the fewer self-contained sub-sets it contains, and the fewer beliefs it dumps into the irrelevant category. Coherence is also increased by our epistemological self-understanding. Why we believe the things we believe, and what we consider to be the standards of "good" justification are important contributors to the explanatory coherence of our belief-set.
However, coherentism does not recognize any epistemological distinction between kinds of beliefs. Specifically, coherentism does not grant any special epistemic status to experiential or perceptual beliefs. The coherence account of knowledge therefore does not provide any necessary linkage between one's network of beliefs and an external reality (that "truth" the essay title speaks of). According to some theorists, the presence in our belief-net of second-order epistemological beliefs about the reliability of our belief forming processes provides experiential observations more weight than might otherwise be supposed. But even with that additional weight, there is nothing within an "explanatory" understanding of "coherence" that necessarily connects our beliefs to the truth. Without granting some special status to observational or experiential beliefs, it is difficult to find a way to ensure that one's coherent set of beliefs maintains some sort of linkage to reality. It is always at least logically possible that there is more than one coherent set of beliefs that might be equally explanatory of the known evidence.
Of course, some coherence theorists take the step of denying that there is any gap between a coherent belief-set and "the truth". The anti-realist concept of truth denies the existence of an evidence-transcendent truth. By adopting such an extremely subjective anti-realist conception of truth, theorists can maintain that reality is defined by, determined by, or otherwise constrained by one's coherent set of beliefs. This is known as the coherence theory of truth. From such a perspective, it is not logically possible for a coherent set of beliefs to not be true. If my beliefs do form a coherent set, they would by definition be true -- making the hypothesis employed in the essay title logically impossible.
However, the obvious abuse of the popular or folk notion of "truth" that such an extremely subjectivist anti-realism introduces usually pushes the anti-realist to generalize the idea in order to make it less subjective. On this broader interpretation, "truth" is the coherent set of beliefs that would be held at the limit of enquiry, or that is held by some particular population, or some omniscient intellect. Unfortunately, this "somewhat realist" retreat from pure subjectivism retains the problematic gap between one's coherent beliefs and the truth. The local belief set of some one individual may be coherent, yet still inconsistent with the broader vision of coherence truth - and therefore not track the truth.
Blanshard argues that there is only one possible coherent set of beliefs, and that set is distinguished from all its rivals by being empirically grounded. According to this approach, the functional purpose of thought and belief formation is to understand our experiences. And to do so by generating the most systematic (coherent) belief-set that explains our experiences. And, I would suppose, to provide the most profitable basis for anticipating the future course of events. So the set of beliefs which we form in the process of understanding our experiences must, because of its starting point in our experiences, be empirically grounded. It is this necessary beginning of belief formation in experience that he claims guarantees that there will be only a single unique set of beliefs which constitutes the most coherent set. Blanshard argues that it is this necessary beginning in experience that guarantees that one's coherence-set of beliefs will track reality (and truth).
However, contra Blanshard, even including the beliefs we form as a result of our efforts at understanding and anticipating our experiences, it is still logically possible that there may be more than one equally good way of incorporating our experiences into a belief set, more than one way of assembling our experiences into a coherent explanatory system. Particularly when we remember that some of our beliefs will be rejected (as anomalous, or erroneous, or irrelevant) along the way. The entire sceptical argument of under-determination is based on the observation that our theories are all under-determined by the evidence. There is always an alternative theory that can explain all our evidence. And no means of distinguishing between them.
As long as the initial premise of a "somewhat realist" notion of truth is maintained, the coherence account of knowledge contains no means of distinguishing between a "reasonable" (ie "in touch with reality") belief-system, and the delusions of a logically adept paranoid. Because it is an internalist theory, the coherence account of knowledge admits no external standard by which to evaluate different belief-systems.
Considering the coherence account of knowledge in the light of Agrippan scepticism and that "somewhat realist" account of truth, focuses attention on the need for beliefs that meet two conditions. First, they must be non-inferentially credible -- justified without deriving their justification from other beliefs. Second, they must be credible in a way that reflects some kind of external constraint. Can we even understand the concept of thinking (not just believing and knowing) if we cannot think of our beliefs as justified in a way that involves the aim of our beliefs being the nature of the world. There are only two ways to anchor a network of beliefs to an external (evidence transcendent) truth. One is to grant some special epistemic status to perceptual / experiential evidence. But down that route lies the competing theory of Foundationalism. The other is to abandon the struggle to maintain pure justification internalism, and allow some external notion such as reliablism to intrude sufficiently to anchor our beliefs. But down that route lies the competing theory of Contextualism.
Once it is acknowledged that the coherence account of knowledge has no means of ensuring that a coherent set of beliefs will track the truth, it must also be recognized that it cannot provide any response against the sceptical challenge that things might be radically different than they seem.
This latter is another very famous radical sceptical challenge to any theory of knowledge. It is known by various names. Most famously it is called "Cartesian Scepticism", after Rene Descartes who initiated modern sceptical thought with his "method of doubt". He hypothesized that for all he knew, all of his experiences might be deceptions provided by an evil demon. More recently, drawing upon the popularity of science fiction and technology, Descartes'evil demon has been replaced by evil scientists or ingenious aliens who steal your brain and place it in a vat of nutrients. In this scenario all of your experiences are provided by a super computer wired to the sensory nerves of your brain.
The Cartesian sceptic argues that all of our beliefs about the existence of an external world are unjustified because all of the evidence (perceptual experience) we have in support of those beliefs cannot rule out the sceptical alternative that we are a brain in a vat. By hypothesis, no experience that we might possibly have can discern whether or not we are a brain in a vat. All of our experiences are therefore fully compatible with both the hypothesis of things being as they seem and the sceptical alternative that we are but a brain in a vat. Hence our beliefs about the external world are unjustified. And since all our beliefs about the external world are unjustified, none can qualify for the honour of "knowledge".
What the Cartesian sceptical challenge depends on is the "prior grounding" model of justification. The "prior grounding" model of justification demands that one be aware of (or at least have access to) the reasons that constitute one's justification in order to validly claim knowledge - the believer himself must possess (and make proper use of) evidence that makes the proposition believed likely to be true. This is a model of justification that is inherent in the explanatory coherence notion that the coherence account of knowledge relies on. Because the coherence account is both internalist and holistic, the knower is assumed to be aware of all of the beliefs that constitute his coherent belief-set, and how they "cohere" together. The Cartesian sceptic argues that because within this belief-set you have no reasons for ruling out the BIV alternative, you cannot justify your belief that you are not a BIV. Hence it is possible that you could in fact be a BIV despite the fact that your belief-set is coherent. As the argument in the ssay title suggests, it is always possible that one's best explanation of (most coherent set of beliefs about) one's experiences might in fact be false.
So on either understanding of the argument in the essay title, it is clear that the coherence account of knowledge must be wrong. It is, at the very least, incomplete.
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