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13. Knowledge Criteria / A. Justification Problems / 1. Justification / c. Defeasibility

[must justification ensure that nothing can defeat it?]

10 ideas
If a grasped perception cannot be shaken by argument, it is 'knowledge' [Zeno of Citium, by Cicero]
If experiential can defeat a belief, then its justification depends on the defeater's absence [Kitcher, by Casullo]
'Overriding' defeaters rule it out, and 'undermining' defeaters weaken in [Casullo]
Knowledge is legitimate only if all relevant defeaters have been eliminated [Fogelin]
The 'defeasibility' approach says true justified belief is knowledge if no undermining facts could be known [Kvanvig]
Can a defeater itself be defeated? [Grundmann]
Simple reliabilism can't cope with defeaters of reliably produced beliefs [Grundmann]
You can 'rebut' previous beliefs, 'undercut' the power of evidence, or 'reason-defeat' the truth [Grundmann]
Knowledge requires that there are no facts which would defeat its justification [Grundmann]
Defeasibility theory needs to exclude defeaters which are true but misleading [Grundmann]