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All the ideas for 'What is Logic?st1=Ian Hacking', 'Reply to 'Rorarius' 2nd ed' and 'The Theory of Communicative Action'

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21 ideas

1. Philosophy / D. Nature of Philosophy / 5. Aims of Philosophy / a. Philosophy as worldly
Habermas seems to make philosophy more democratic [Habermas, by Bowie]
     Full Idea: Habermas is concerned to avoid the traumas of modern German history by making democracy an integral part of philosophy.
     From: report of Jürgen Habermas (The Theory of Communicative Action [1981]) by Andrew Bowie - Introduction to German Philosophy Conc 'Habermas'
     A reaction: Hence Habermas's emphasis on communication as central to language, which is central to philosophy. Modern philosophy departments are amazingly hierarchical.
1. Philosophy / E. Nature of Metaphysics / 4. Metaphysics as Science
The aim of 'post-metaphysical' philosophy is to interpret the sciences [Habermas, by Finlayson]
     Full Idea: For Habermas, the task of what he calls 'post-metaphysical' philosophy is to be a stand-in and interpreter for the specialized sciences.
     From: report of Jürgen Habermas (The Theory of Communicative Action [1981]) by James Gordon Finlayson - Habermas Ch.5:65
1. Philosophy / H. Continental Philosophy / 5. Critical Theory
We can do social philosophy by studying coordinated action through language use [Habermas, by Finlayson]
     Full Idea: Habermas claims to have embarked upon a new way of doing social philosophy, one that begins from an analysis of language use and that locates the rational basis of the coordination of action in speech.
     From: report of Jürgen Habermas (The Theory of Communicative Action [1981]) by James Gordon Finlayson - Habermas Ch.3:28
2. Reason / A. Nature of Reason / 4. Aims of Reason
Rather than instrumental reason, Habermas emphasises its communicative role [Habermas, by Oksala]
     Full Idea: Instead of Enlightenment instrumental rationality (criticised by Adorno and Horkheimer), Habermas emphasizes 'communicative rationality', which makes critical discussion and mutual understanding possible.
     From: report of Jürgen Habermas (The Theory of Communicative Action [1981]) by Johanna Oksala - Political Philosophy: all that matters Ch.6
     A reaction: There was a good reason not to smoke cigarettes, before we found out what it is. In one sense, reasons are in the world. This is interesting, but I feel analytic vertigo, as the lovely concept of 'rationality' becomes blurred and diffused.
2. Reason / D. Definition / 3. Types of Definition
A decent modern definition should always imply a semantics [Hacking]
     Full Idea: Today we expect that anything worth calling a definition should imply a semantics.
     From: Ian Hacking (What is Logic? [1979], §10)
     A reaction: He compares this with Gentzen 1935, who was attempting purely syntactic definitions of the logical connectives.
4. Formal Logic / B. Propositional Logic PL / 2. Tools of Propositional Logic / d. Basic theorems of PL
'Thinning' ('dilution') is the key difference between deduction (which allows it) and induction [Hacking]
     Full Idea: 'Dilution' (or 'Thinning') provides an essential contrast between deductive and inductive reasoning; for the introduction of new premises may spoil an inductive inference.
     From: Ian Hacking (What is Logic? [1979], §06.2)
     A reaction: That is, inductive logic (if there is such a thing) is clearly non-monotonic, whereas classical inductive logic is monotonic.
Gentzen's Cut Rule (or transitivity of deduction) is 'If A |- B and B |- C, then A |- C' [Hacking]
     Full Idea: If A |- B and B |- C, then A |- C. This generalises to: If Γ|-A,Θ and Γ,A |- Θ, then Γ |- Θ. Gentzen called this 'cut'. It is the transitivity of a deduction.
     From: Ian Hacking (What is Logic? [1979], §06.3)
     A reaction: I read the generalisation as 'If A can be either a premise or a conclusion, you can bypass it'. The first version is just transitivity (which by-passes the middle step).
Only Cut reduces complexity, so logic is constructive without it, and it can be dispensed with [Hacking]
     Full Idea: Only the cut rule can have a conclusion that is less complex than its premises. Hence when cut is not used, a derivation is quite literally constructive, building up from components. Any theorem obtained by cut can be obtained without it.
     From: Ian Hacking (What is Logic? [1979], §08)
5. Theory of Logic / A. Overview of Logic / 4. Pure Logic
The various logics are abstractions made from terms like 'if...then' in English [Hacking]
     Full Idea: I don't believe English is by nature classical or intuitionistic etc. These are abstractions made by logicians. Logicians attend to numerous different objects that might be served by 'If...then', like material conditional, strict or relevant implication.
     From: Ian Hacking (What is Logic? [1979], §15)
     A reaction: The idea that they are 'abstractions' is close to my heart. Abstractions from what? Surely 'if...then' has a standard character when employed in normal conversation?
5. Theory of Logic / A. Overview of Logic / 5. First-Order Logic
First-order logic is the strongest complete compact theory with Löwenheim-Skolem [Hacking]
     Full Idea: First-order logic is the strongest complete compact theory with a Löwenheim-Skolem theorem.
     From: Ian Hacking (What is Logic? [1979], §13)
A limitation of first-order logic is that it cannot handle branching quantifiers [Hacking]
     Full Idea: Henkin proved that there is no first-order treatment of branching quantifiers, which do not seem to involve any idea that is fundamentally different from ordinary quantification.
     From: Ian Hacking (What is Logic? [1979], §13)
     A reaction: See Hacking for an example of branching quantifiers. Hacking is impressed by this as a real limitation of the first-order logic which he generally favours.
5. Theory of Logic / A. Overview of Logic / 7. Second-Order Logic
Second-order completeness seems to need intensional entities and possible worlds [Hacking]
     Full Idea: Second-order logic has no chance of a completeness theorem unless one ventures into intensional entities and possible worlds.
     From: Ian Hacking (What is Logic? [1979], §13)
5. Theory of Logic / E. Structures of Logic / 2. Logical Connectives / a. Logical connectives
With a pure notion of truth and consequence, the meanings of connectives are fixed syntactically [Hacking]
     Full Idea: My doctrine is that the peculiarity of the logical constants resides precisely in that given a certain pure notion of truth and consequence, all the desirable semantic properties of the constants are determined by their syntactic properties.
     From: Ian Hacking (What is Logic? [1979], §09)
     A reaction: He opposes this to Peacocke 1976, who claims that the logical connectives are essentially semantic in character, concerned with the preservation of truth.
5. Theory of Logic / E. Structures of Logic / 4. Variables in Logic
Perhaps variables could be dispensed with, by arrows joining places in the scope of quantifiers [Hacking]
     Full Idea: For some purposes the variables of first-order logic can be regarded as prepositions and place-holders that could in principle be dispensed with, say by a system of arrows indicating what places fall in the scope of which quantifier.
     From: Ian Hacking (What is Logic? [1979], §11)
     A reaction: I tend to think of variables as either pronouns, or as definite descriptions, or as temporary names, but not as prepositions. Must address this new idea...
5. Theory of Logic / J. Model Theory in Logic / 3. Löwenheim-Skolem Theorems
If it is a logic, the Löwenheim-Skolem theorem holds for it [Hacking]
     Full Idea: A Löwenheim-Skolem theorem holds for anything which, on my delineation, is a logic.
     From: Ian Hacking (What is Logic? [1979], §13)
     A reaction: I take this to be an unusually conservative view. Shapiro is the chap who can give you an alternative view of these things, or Boolos.
12. Knowledge Sources / A. A Priori Knowledge / 11. Denying the A Priori
What is considered a priori changes as language changes [Habermas, by Bowie]
     Full Idea: Habermas claims that what is regarded as a priori changes with history. This is because the linguistic structures on which judgements depend are themselves part of history, not prior to it.
     From: report of Jürgen Habermas (The Theory of Communicative Action [1981]) by Andrew Bowie - Introduction to German Philosophy Conc 'Habermas'
     A reaction: This is an interesting style of argument generally only found in continental philosophers, because they see the problem as historical rather than timeless. Compare Idea 20595, which sees analyticity historically.
19. Language / A. Nature of Meaning / 1. Meaning
To understand a statement is to know what would make it acceptable [Habermas]
     Full Idea: We understand the meaning of a speech act when we know what would make it acceptable.
     From: Jürgen Habermas (The Theory of Communicative Action [1981], I:297), quoted by James Gordon Finlayson - Habermas Ch.3:37
     A reaction: Finlayson glosses this as requiring the reasons which would justify the speech act.
19. Language / A. Nature of Meaning / 3. Meaning as Speaker's Intention
Meaning is not fixed by a relation to the external world, but a relation to other speakers [Habermas, by Finlayson]
     Full Idea: On Habermas's view, meanings are not determined by the speaker's relation to the external world, but by his relation to his interlocutors; meaning is essentially intersubjective.
     From: report of Jürgen Habermas (The Theory of Communicative Action [1981]) by James Gordon Finlayson - Habermas Ch.3:38
     A reaction: This view is not the same as Grice's, but it is clearly much closer to Grice than to (say) the Frege/Davidson emphasis on truth-conditions. I'm not sure if I would know how to begin arbitrating between the two views!
24. Political Theory / D. Ideologies / 6. Liberalism / a. Liberalism basics
People endorse equality, universality and inclusiveness, just by their communicative practices [Habermas, by Finlayson]
     Full Idea: The ideal of equality, universality, and inclusiveness are inscribed in the communicative practices of the lifeworld, and agents, merely by virtue of communicating, conform to them.
     From: report of Jürgen Habermas (The Theory of Communicative Action [1981]) by James Gordon Finlayson - Habermas Ch.4:60
     A reaction: This summary of Habermas's social views strikes me as thoroughly Kantian. It is something like the ideals of the Kingdom of Ends, necessarily implemented in a liberal society. Habermas emphasises the social, where Kant starts from the liberal.
25. Social Practice / B. Equalities / 2. Political equality
Political involvement is needed, to challenge existing practices [Habermas, by Kymlicka]
     Full Idea: Habermas thinks political deliberation is required precisely because in its absence people will tend to accept existing practices as given, and thereby perpetuate false needs.
     From: report of Jürgen Habermas (The Theory of Communicative Action [1981]) by Will Kymlicka - Community 'need'
     A reaction: If the dream is healthy and intelligent progress, it is not clear where that should come from. The problem with state involvement in the authority and power of the state. Locals are often prejudiced, so the intermediate level may be best.
27. Natural Reality / D. Time / 1. Nature of Time / b. Relative time
Space and time are the order of all possibilities, and don't just relate to what is actual [Leibniz]
     Full Idea: Space and time taken together constitute the order of possibilities of the one entire universe, so that these orders relate not only to what actually is, but also to anything that could be put in its place.
     From: Gottfried Leibniz (Reply to 'Rorarius' 2nd ed [1702], GP iv 568), quoted by Richard T.W. Arthur - Leibniz 7 'Space and Time'
     A reaction: A very nice idea. Rather like the 'space of reasons', where all rational thought must exist, space and time are the 'space of existence and action'. Their concepts involve more than relations between what actually exists.