Ideas of Rudolph Carnap, by Theme

[German, 1891 - 1970, Born at Ronsdorf, Germany. Pupil of Frege. Taught at the University of California. Quine and Kaplan were pupils.]

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1. Philosophy / E. Nature of Metaphysics / 2. Possibility of Metaphysics
No possible evidence could decide the reality of numbers, so it is a pseudo-question
     Full Idea: I cannot think of any possible evidence that would be regarded as relevant by both nominalists and realists about numbers, and would decide the controversy, or make one side more probable. Hence I regard the external questions as pseudo-questions.
     From: Rudolph Carnap (Empiricism, Semantics and Ontology [1950], 4)
1. Philosophy / E. Nature of Metaphysics / 7. Against Metaphysics
Metaphysics uses empty words, or just produces pseudo-statements
     Full Idea: Since metaphysics doesn't want to assert analytic propositions, nor fall within the domain of physical science, it is compelled to employ words for which no criteria of application are specified, ..or else combine meaningful words..into pseudo-statements.
     From: Rudolph Carnap (Elimination of Metaphysics by Analysis of Language [1959]), quoted by Tim Maudlin - The Metaphysics within Physics 2.4
     A reaction: A classic summary of the logical positivist rejection of metaphysics. I incline to treat metaphysics as within the domain of science, but at a level of generality so high that practising scientists become bewildered and give up.
5. Theory of Logic / B. Logical Consequence / 1. Logical Consequence
Carnap defined consequence by contradiction, but this is unintuitive and changes with substitution
     Full Idea: Carnap proposed to define consequence as 'sentence X follows from the sentences K iff the sentences K and the negation of X are contradictory', but 1) this is intuitively impossible, and 2) consequence would be changed by substituting objects.
     From: comment on Rudolph Carnap (The Logical Syntax of Language [1934], p.88-) by Alfred Tarski - The Concept of Logical Consequence p.414
     A reaction: This seems to be the first step in the ongoing explicit discussion of the nature of logical consequence, which is now seen by many as the central concept of logic. Tarski brings his new tool of 'satisfaction' to bear.
5. Theory of Logic / C. Ontology of Logic / 4. Logic by Convention
Each person is free to build their own logic, just by specifying a syntax
     Full Idea: In logic, there are no morals. Everyone is at liberty to build his own logic, i.e. his own form of language. All that is required is that he must state his methods clearly, and give syntactical rules instead of philosophical arguments.
     From: Rudolph Carnap (The Logical Syntax of Language [1934], §17), quoted by JC Beall / G Restall - Logical Pluralism 7.3
     A reaction: This is understandable, but strikes me as close to daft relativism. If I specify a silly logic, I presume its silliness will be obvious. By what criteria? I say the world dictates the true logic, but this is a minority view.
6. Mathematics / C. Sources of Mathematics / 6. Logicism / a. Early logicism
Questions about numbers are answered by analysis, and are analytic, and hence logically true
     Full Idea: For the internal question like 'is there a prime number greater than a hundred?' the answers are found by logical analysis based on the rules for the new expressions. The answers here are analytic, i.e., logically true.
     From: Rudolph Carnap (Empiricism, Semantics and Ontology [1950], 2)
Logical positivists incorporated geometry into logicism, saying axioms are just definitions
     Full Idea: The logical positivists brought geometry into the fold of logicism. The axioms of, say, Euclidean geometry are simply definitions of primitive terms like 'point' and 'line'.
     From: report of Rudolph Carnap (Empiricism, Semantics and Ontology [1950]) by Stewart Shapiro - Thinking About Mathematics 5.3
     A reaction: If the concept of 'line' is actually created by its definition, then we need to know exactly what (say) 'shortest' means. If we are merely describing a line, then our definition can be 'impredicative', using other accepted concepts.
7. Existence / A. Nature of Existence / 4. Abstract Existence
Internal questions about abstractions are trivial, and external ones deeply problematic
     Full Idea: Carnap's verdict is that questions regarding the existence of abstracta tend to be trivial when taken as internal and deeply problematic when taken as external.
     From: report of Rudolph Carnap (Empiricism, Semantics and Ontology [1950]) by Zoltán Gendler Szabó - Nominalism 6
     A reaction: If the internal aspect of the problem is 'trivial', this would put Carnap in league with fictionalists, who are only committed to entities while playing the current game. What is the status of the theory? Carnap wanted flowers to bloom.
7. Existence / D. Theories of Reality / 1. Ontologies
Existence questions are 'internal' (within a framework) or 'external' (concerning the whole framework)
     Full Idea: We distinguish two kinds of existence questions: first, entities of a new kind within the framework; we call them 'internal questions'. Second, 'external questions', concerning the existence or reality of the system of entities as a whole.
     From: Rudolph Carnap (Empiricism, Semantics and Ontology [1950], 2)
     A reaction: This nicely disposes of many ontological difficulties, but at the price of labelling most external questions as meaningless, so that the internal answers have very little commitment, and the external (big) questions are now banned. Not for me.
7. Existence / D. Theories of Reality / 3. Reality
To be 'real' is to be an element of a system, so we cannot ask reality questions about the system itself
     Full Idea: To be real in the scientific sense means to be an element of the system; hence this concept cannot be meaningfully applied to the system itself.
     From: Rudolph Carnap (Empiricism, Semantics and Ontology [1950], 2)
7. Existence / D. Theories of Reality / 11. Ontological Commitment / a. Ontological commitment
A linguistic framework involves commitment to entities, so only commitment to the framework is in question
     Full Idea: If someone accepts a framework for a kind of entities, then he must admit the entities as possible designata. Thus the question of the admissibility of entities is reduced to the question of the acceptability of the linguistic framework for the entities.
     From: Rudolph Carnap (Empiricism, Semantics and Ontology [1950], 4)
     A reaction: Despite the many differences of opinion between Quine and Carnap, this appears to be a straight endorsement by Carnap of the Quinean conception of ontological commitment.
9. Objects / A. Existence of Objects / 6. Nihilism about Objects
We only accept 'things' within a language with formation, testing and acceptance rules
     Full Idea: To accept the thing world means nothing more than to accept a certain form of language, in other words, to accept rules for forming statements and for testing, accepting, or rejecting them.
     From: Rudolph Carnap (Empiricism, Semantics and Ontology [1950], 2)
     A reaction: If you derive your metaphysics from your language, then objects are linguistic conventions. But why do we accept conventions about objects?
10. Modality / B. Possibility / 8. Conditionals / c. Truth-function conditionals
In the truth-functional account a burnt-up match was soluble because it never entered water
     Full Idea: If a wooden match was completely burned up yesterday, and never placed in water at any time, is it not the case, therefore, that the match is soluble (in the truth-functional view). This follows just from the antecedent being false.
     From: Rudolph Carnap (Testability and Meaning [1937], I.440), quoted by Stephen Mumford - Dispositions
     A reaction: This, along with Edgington's nice example of the conditional command (Idea ) seems conclusive against the truth-functional account. The only defence possible is some sort of pragmatic account about implicature.
12. Knowledge Sources / D. Empiricism / 1. Empiricism
Empiricists tend to reject abstract entities, and to feel sympathy with nominalism
     Full Idea: Empiricists are in general rather suspicious with respect to any kind of abstract entities like properties, classes, relations, numbers, propositions etc. They usually feel more sympathy with nominalists than with realists (in the medieval sense).
     From: Rudolph Carnap (Empiricism, Semantics and Ontology [1950], 1)
     A reaction: The obvious reason is that you can't have sense experiences of abstract entities. I like the question 'what are they made of?' rather than the question 'how can I experience them?'.
12. Knowledge Sources / D. Empiricism / 3. Pragmatism
New linguistic claims about entities are not true or false, but just expedient, fruitful or successful
     Full Idea: The acceptance of new linguistic forms about entities cannot be judged as being either true or false because it is not an assertion. It can only be judged as being more or less expedient, fruitful, conducive to the aim for which the language is intended.
     From: Rudolph Carnap (Empiricism, Semantics and Ontology [1950], 3)
     A reaction: The obvious problem seems to be that a complete pack of lies might be successful for a very long time, if it plugged a critical hole in a major theory. Is success judged financially? How do we judge success without mentioning truth?
14. Science / B. Scientific Theories / 1. Scientific Theory
Carnap tried to define all scientific predicates in terms of primitive relations, using type theory
     Full Idea: Carnap's ultimate ambition in the Aufbau is to provide a constitution-system within which any predicate of any scientific vocabulary can be explicitly defined in terms of primitive relations holding among basic elements, using type theory.
     From: report of Rudolph Carnap (The Logical Structure of the World (Aufbau) [1928]) by Tim Button - The Limits of Reason 05.2
     A reaction: David Chalmers has a modern shot at the same project in 'Constructing the World'. Ramsey sentences seem to be part of the same game.
14. Science / B. Scientific Theories / 3. Instrumentalism
All linguistic forms in science are merely judged by their efficiency as instruments
     Full Idea: The acceptance or rejection of abstract (or any other) linguistic forms in any branch of science will finally be decided by their efficiency as instruments.
     From: Rudolph Carnap (Empiricism, Semantics and Ontology [1950], 5)
14. Science / D. Explanation / 1. Explanation / b. Aims of explanation
Good explications are exact, fruitful, simple and similar to the explicandum
     Full Idea: Carnap's four criteria for giving a good explication are similarity to the explicandum, exactness, fruitfulness and simplicity.
     From: report of Rudolph Carnap (Logical Foundations of Probability [1950], Ch.1) by Wesley Salmon - Four Decades of Scientific Explanation 0.1
     A reaction: [compressed] Salmon's view is that this represents the old attitude, that the contribution of philosophy to explanation is the clarification of the key concepts. Carnap is, of course, a logical empiricist.
18. Thought / D. Concepts / 4. Structure of Concepts / g. Conceptual atomism
All concepts can be derived from a few basics, making possible one science of everything
     Full Idea: In the 'Aufbau', Carnap tried to show how all of our concepts can be derived from a few basic concepts. ..Consequently there can be one science which studied all that existed, the science of the objects corresponding to the basic concepts.
     From: report of Rudolph Carnap (The Logical Structure of the World (Aufbau) [1928]) by Baruch Brody - Identity and Essence 2.2
     A reaction: This is Carnap's Constructionist programme.
19. Language / C. Assigning Meanings / 8. Possible Worlds Semantics
The intension of a sentence is the set of all possible worlds in which it is true
     Full Idea: Carnap's proposal is to understand the category of intensions appropriate to sentences (his 'propositions') as sets of possible worlds. The intension of the sentence is taken as the set of all possible worlds in which the sentence is true.
     From: report of Rudolph Carnap (Meaning and Necessity [1947]) by David Kaplan - Transworld Heir Lines p.90
     A reaction: [reference?] This extension of the truth-conditions view of meaning strikes me as being very attractive. Except that whole worlds hardly seem to be relevant to my remark about how lunch might have been improved.
19. Language / F. Communication / 6. Interpreting Language / a. Translation
All translation loses some content (but language does not create reality)
     Full Idea: I do not believe in translatability without loss of content, and therefore I think that the content of a world description is influenced to a certain degree by choice of a language form. But that does not mean that reality is created through language.
     From: Rudolph Carnap (Letters to Schlick [1935], 1935.12.04), quoted by J. Alberto Coffa - The Semantic Tradition from Kant to Carnap 19 'Truth'
     A reaction: It is a mistake to think Quine was the first to spot the interest of translation in philosophy of language. 'Does translation always lose content?' is a very nice question for focusing the problem.