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'works', 'The Establishment of Scientific Semantics' and 'Begriffsschrift'
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17 ideas
5. Theory of Logic / A. Overview of Logic / 1. Overview of Logic
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7728
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Frege has a judgement stroke (vertical, asserting or judging) and a content stroke (horizontal, expressing) [Frege, by Weiner]
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16881
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The laws of logic are boundless, so we want the few whose power contains the others [Frege]
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5. Theory of Logic / A. Overview of Logic / 2. History of Logic
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7622
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In 1879 Frege developed second order logic [Frege, by Putnam]
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5. Theory of Logic / A. Overview of Logic / 6. Classical Logic
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13337
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A language: primitive terms, then definition rules, then sentences, then axioms, and finally inference rules [Tarski]
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5. Theory of Logic / E. Structures of Logic / 1. Logical Form
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7729
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Frege replaced Aristotle's subject/predicate form with function/argument form [Frege, by Weiner]
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5. Theory of Logic / G. Quantification / 1. Quantification
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9950
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A quantifier is a second-level predicate (which explains how it contributes to truth-conditions) [Frege, by George/Velleman]
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5. Theory of Logic / G. Quantification / 2. Domain of Quantification
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9991
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For Frege the variable ranges over all objects [Frege, by Tait]
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10536
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Frege's domain for variables is all objects, but modern interpretations first fix the domain [Dummett on Frege]
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5. Theory of Logic / G. Quantification / 3. Objectual Quantification
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7730
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Frege introduced quantifiers for generality [Frege, by Weiner]
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7742
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Frege reduced most quantifiers to 'everything' combined with 'not' [Frege, by McCullogh]
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5. Theory of Logic / H. Proof Systems / 1. Proof Systems
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13824
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Proof theory began with Frege's definition of derivability [Frege, by Prawitz]
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5. Theory of Logic / H. Proof Systems / 2. Axiomatic Proof
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13609
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Frege produced axioms for logic, though that does not now seem the natural basis for logic [Frege, by Kaplan]
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5. Theory of Logic / I. Semantics of Logic / 1. Semantics of Logic
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13335
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Semantics is the concepts of connections of language to reality, such as denotation, definition and truth [Tarski]
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13336
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A language containing its own semantics is inconsistent - but we can use a second language [Tarski]
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5. Theory of Logic / I. Semantics of Logic / 4. Satisfaction
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13339
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A sentence is satisfied when we can assert the sentence when the variables are assigned [Tarski]
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13340
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Satisfaction is the easiest semantical concept to define, and the others will reduce to it [Tarski]
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5. Theory of Logic / K. Features of Logics / 2. Consistency
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13341
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Using the definition of truth, we can prove theories consistent within sound logics [Tarski]
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