Combining Philosophers
Ideas for Hermarchus, Michael Potter and Augustus De Morgan
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8 ideas
5. Theory of Logic / A. Overview of Logic / 7. Second-Order Logic
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10704
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We can formalize second-order formation rules, but not inference rules [Potter]
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5. Theory of Logic / B. Logical Consequence / 3. Deductive Consequence |-
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22279
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Frege's sign |--- meant judgements, but the modern |- turnstile means inference, with intecedents [Potter]
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5. Theory of Logic / C. Ontology of Logic / 3. If-Thenism
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22291
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Deductivism can't explain how the world supports unconditional conclusions [Potter]
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5. Theory of Logic / E. Structures of Logic / 6. Relations in Logic
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17744
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De Morgan started the study of relations and their properties [De Morgan, by Walicki]
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13501
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De Morgan found inferences involving relations, which eluded Aristotle's syllogistic [De Morgan, by Hart,WD]
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5. Theory of Logic / G. Quantification / 2. Domain of Quantification
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17743
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De Morgan introduced a 'universe of discourse', to replace Boole's universe of 'all things' [De Morgan, by Walicki]
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5. Theory of Logic / H. Proof Systems / 3. Proof from Assumptions
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10703
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Supposing axioms (rather than accepting them) give truths, but they are conditional [Potter]
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5. Theory of Logic / I. Semantics of Logic / 3. Logical Truth
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22295
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Modern logical truths are true under all interpretations of the non-logical words [Potter]
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