Remarks on Two Papers of Paul Bernays
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Charles Parsons
Abstract
The paper comments on two papers in French that Paul Bernays derived from lectures at a conference on mathematical logic held in Geneva in June 1934. The first, the well-known “On Platonism in mathematics,” sets forth a methodological version of Platonism and observes that it can be implemented in some branches of mathematics and not others. He notes that by his definition Brouwer’s intuitionism rejects all Platonism,while HermannWeyl’s reconstruction of analysis retains it for generalizations about natural numbers but not for generalizations about real numbers or higher-type objects. He rejects the then widespread idea of a crisis of foundations and argues that the questions raised are philosophical. Bernays’ second paper, “Some observations on metamathematics,” is a technical sequel to “On Platonism.” It describes some basic points in the Hilbert school’s proof theory and sketches some results, such as a simple application of Herbrand’s theorem, Gödel’s proof that if intuitionistic first-order arithmetic is consistent, then so is classical, and Gödel’s second incompleteness theorem. A full proof of the latter and a correct proof of Herbrand’s theorem only appeared in 1939, in volume II of Hilbert and Bernays, Grundlagen der Mathematik.
Abstract
The paper comments on two papers in French that Paul Bernays derived from lectures at a conference on mathematical logic held in Geneva in June 1934. The first, the well-known “On Platonism in mathematics,” sets forth a methodological version of Platonism and observes that it can be implemented in some branches of mathematics and not others. He notes that by his definition Brouwer’s intuitionism rejects all Platonism,while HermannWeyl’s reconstruction of analysis retains it for generalizations about natural numbers but not for generalizations about real numbers or higher-type objects. He rejects the then widespread idea of a crisis of foundations and argues that the questions raised are philosophical. Bernays’ second paper, “Some observations on metamathematics,” is a technical sequel to “On Platonism.” It describes some basic points in the Hilbert school’s proof theory and sketches some results, such as a simple application of Herbrand’s theorem, Gödel’s proof that if intuitionistic first-order arithmetic is consistent, then so is classical, and Gödel’s second incompleteness theorem. A full proof of the latter and a correct proof of Herbrand’s theorem only appeared in 1939, in volume II of Hilbert and Bernays, Grundlagen der Mathematik.
Chapters in this book
- Frontmatter I
- Contents V
- Preface IX
-
Part I: Philosophy of Logic
- Link’s Revenge: A Case Study in Natural Language Mereology 3
- Universal Translatability: An Optimality- Based Justification of (Classical) Logic 37
- Invariance and Necessity 55
- Translations Between Logics: A Survey 71
- On the Relation of Logic to Metalogic 91
- Free Logic and the Quantified Argument Calculus 105
- Dependencies Between Quantifiers Vs. Dependencies Between Variables 117
- Three Types and Traditions of Logic: Syllogistic, Calculus and Predicate Logic 133
- Truth, Paradox, and the Procedural Conception of Fregean Sense 153
- Wittgenstein and Frege on Assertion 169
- Assertions and Their Justification: Demonstration and Self-Evidence 183
- Surprises in Logic: When Dynamic Formality Meets Interactive Compositionality 197
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Part II: Philosophy of Mathematics
- Neologicist Foundations: Inconsistent Abstraction Principles and Part-Whole 215
- What Hilbert and Bernays Meant by “Finitism” 249
- Wittgenstein and Turing 263
- Remarks on Two Papers of Paul Bernays 297
- The Significance of the Curry-Howard Isomorphism 313
- Reductions of Mathematics: Foundation or Horizon? 327
- What Are the Axioms for Numbers and Who Invented Them? 343
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Part III: Wittgenstein
- Following a Rule: Waismann’s Variation 359
- Propositions in Wittgenstein and Ramsey 375
- An Unexpected Feature of Classical Propositional Logic in the Tractatus 385
- Ontology in Tractatus Logico-Philosophicus: A Topological Approach 397
- Adding 4.0241 to TLP 415
- Understanding Wittgenstein’s Wood Sellers 429
- On the Infinite, In-Potentia: Discovery of the Hidden Revision of Philosophical Investigations and Its Relation to TS 209 Through the Eyes of Wittgensteinian Mathematics 441
- Incomplete Pictures and Specific Forms: Wittgenstein Around 1930 457
- „Man kann die Menschen nicht zum Guten führen“ – Zur Logik des moralischen Urteils bei Wittgenstein und Hegel 473
- Der Status mathematischer und religiöser Sätze bei Wittgenstein 485
- Gutes Sehen 499
- Wittgenstein’s Conjecture 515
- Index of Names 535
- Index of Subjects 539
Chapters in this book
- Frontmatter I
- Contents V
- Preface IX
-
Part I: Philosophy of Logic
- Link’s Revenge: A Case Study in Natural Language Mereology 3
- Universal Translatability: An Optimality- Based Justification of (Classical) Logic 37
- Invariance and Necessity 55
- Translations Between Logics: A Survey 71
- On the Relation of Logic to Metalogic 91
- Free Logic and the Quantified Argument Calculus 105
- Dependencies Between Quantifiers Vs. Dependencies Between Variables 117
- Three Types and Traditions of Logic: Syllogistic, Calculus and Predicate Logic 133
- Truth, Paradox, and the Procedural Conception of Fregean Sense 153
- Wittgenstein and Frege on Assertion 169
- Assertions and Their Justification: Demonstration and Self-Evidence 183
- Surprises in Logic: When Dynamic Formality Meets Interactive Compositionality 197
-
Part II: Philosophy of Mathematics
- Neologicist Foundations: Inconsistent Abstraction Principles and Part-Whole 215
- What Hilbert and Bernays Meant by “Finitism” 249
- Wittgenstein and Turing 263
- Remarks on Two Papers of Paul Bernays 297
- The Significance of the Curry-Howard Isomorphism 313
- Reductions of Mathematics: Foundation or Horizon? 327
- What Are the Axioms for Numbers and Who Invented Them? 343
-
Part III: Wittgenstein
- Following a Rule: Waismann’s Variation 359
- Propositions in Wittgenstein and Ramsey 375
- An Unexpected Feature of Classical Propositional Logic in the Tractatus 385
- Ontology in Tractatus Logico-Philosophicus: A Topological Approach 397
- Adding 4.0241 to TLP 415
- Understanding Wittgenstein’s Wood Sellers 429
- On the Infinite, In-Potentia: Discovery of the Hidden Revision of Philosophical Investigations and Its Relation to TS 209 Through the Eyes of Wittgensteinian Mathematics 441
- Incomplete Pictures and Specific Forms: Wittgenstein Around 1930 457
- „Man kann die Menschen nicht zum Guten führen“ – Zur Logik des moralischen Urteils bei Wittgenstein und Hegel 473
- Der Status mathematischer und religiöser Sätze bei Wittgenstein 485
- Gutes Sehen 499
- Wittgenstein’s Conjecture 515
- Index of Names 535
- Index of Subjects 539