Certainty (n.) is actually presupposed in any attempt at doubting.
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Certainty (n.) is, as it were, a tone of voice, one in which one declares how things are.
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Certainty (n.) is not about propositions but is about a foundational way of acting which underpins our epistemic activity.
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Certainty (n.) suggests that logic makes it impossible to experience going wrong.
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Certainty (n.) lies beyond being justified or unjustified — as it were, something animal.