I believe: (1) it is raining outside, (2) the streets are wet, (3) wet streets cause accidents, (4) I should drive carefully. Which of the following additions to this belief system would demonstrate coherence in the philosophically relevant sense?
AI also believe that 7 is a prime number, which is logically consistent with all four beliefs
BI also believe that driving carefully reduces accident risk, which connects explanatorily to beliefs 3 and 4
CI also believe that Napoleon lost at Waterloo, which does not contradict any of the four beliefs
DI also believe that the moon is made of cheese, since this belief is not explicitly ruled out by the others
Coherentism requires more than logical consistency — options A, C, and D all describe beliefs that are merely consistent (no contradictions) but have no explanatory or probabilistic connections to the existing beliefs. Only option B adds genuine coherence: the new belief connects to and mutually supports existing beliefs through an explanatory relationship. This is the key misconception the topic warns against: coherence is not the absence of contradiction but the presence of mutual support and integration.
Question 2 Multiple Choice
A philosopher argues: 'I could construct a perfectly internally consistent, explanatorily rich fantasy world — every belief about it coheres beautifully with every other — yet this system is clearly not knowledge, because it has no connection to the actual world.' This objection targets coherentism by invoking which problem?
AThe regress problem — coherentism cannot stop the infinite chain of justification
BThe Gettier problem — justified true belief can still fail to be knowledge
CThe input problem — a coherent system might be entirely disconnected from reality
DThe circularity problem — coherentism allows any belief to justify itself
This is the input problem (also called the isolation objection): if justification is purely a matter of internal coherence, then a maximally coherent system that is entirely unmoored from reality would appear to be justified. The objection is that knowledge must be anchored to the world somehow, not just internally tidy. Coherentists respond that sensory experiences are incorporated into the web, not left outside — but this is exactly the pressure point that divides coherentism from externalist views.
Question 3 True / False
According to coherentism, a belief is justified if and only if it does not contradict any other belief you hold.
TTrue
FFalse
Answer: False
This conflates coherence with mere logical consistency, which is one of the core misconceptions the topic identifies. Logical consistency means only that no two beliefs are contradictory. But coherence in the relevant sense requires *mutual support*: beliefs should entail each other, provide probabilistic support, explain each other, and integrate into a structure. Two beliefs can be perfectly consistent yet have no coherence — 'Napoleon lost at Waterloo' and 'pi is approximately 3.14' are consistent but unrelated, contributing nothing to each other's justification.
Question 4 True / False
The coherentist holds that revising one belief in the web can sometimes require revising other beliefs, because beliefs are connected by logical entailment, probabilistic support, and explanatory relationships.
TTrue
FFalse
Answer: True
This holistic interdependence is precisely what Quine's 'web of belief' metaphor captures. Beliefs are not epistemically isolated — they face experience as a 'corporate body.' Revising a central belief (say, a fundamental physical law) would require revising vast portions of the web because so much else depends on it. Revising a peripheral belief (a particular perceptual claim) requires less adjustment. This interconnection is what makes justification holistic rather than linear or foundational.
Question 5 Short Answer
What is the input problem for coherentism, and why is it considered such a serious challenge?
Think about your answer, then reveal below.
Model answer: The input problem is the objection that a belief system could be internally coherent — consistent, explanatorily integrated, mutually supporting — while being entirely disconnected from reality. If coherentism makes justification purely a matter of internal relations, then a self-consistent fantasy or paranoid delusion would appear to qualify as justified belief, even knowledge. This is serious because it suggests coherentism cannot distinguish between a well-functioning epistemic system that tracks reality and one that merely 'hangs together' in isolation.
The input problem marks the real fault line between coherentism and externalist views (like reliabilism) that require a more direct connection between justification and truth. Coherentists respond that sensory experiences are not inputs from outside the web but beliefs within it — perceptual experiences enter the web as observational beliefs, anchoring it to the world. But critics find this response unsatisfying: if experience is just another belief to be adjudicated by coherence, what prevents the system from re-interpreting recalcitrant experience to maintain its coherence rather than revising the web?