17 ideas
| 13838 | 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. |
| 13833 | '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. |
| 13834 | 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). |
| 13835 | 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) |
| 13845 | 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? |
| 13840 | 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) |
| 13844 | 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. |
| 13842 | 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) |
| 13837 | 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. |
| 13839 | 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... |
| 13843 | 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. |
| 468 | Musical performance can reveal a range of virtues [Damon of Ath.] |
| Full Idea: In singing and playing the lyre, a boy will be likely to reveal not only courage and moderation, but also justice. | |
| From: Damon (fragments/reports [c.460 BCE], B4), quoted by (who?) - where? |
| 22262 | Kant's moral law has no foundation - because that would undermine its priority [Sandel] |
| Full Idea: Given the stringent demands of the Kantian ethic, the moral law would seem almost to require a foundation in nothing, for any empirical precondition would undermine its priority. | |
| From: Michael J. Sandel (Procedural republic and unencumbered self [1984], 'Kantian') | |
| A reaction: The idea of a value with 'a foundation in nothing' is particular anathema to me, because my project is to find a foundation for everything (in nature, which is the Given). Kant's only foundational value seems to be rational consistency. |
| 22264 | Modern liberal rights in democracies protect individuals against the majority [Sandel] |
| Full Idea: Liberty in the modern procedural republic is defined in opposition to democracy, as an individual's guarantee against what the majority might will. | |
| From: Michael J. Sandel (Procedural republic and unencumbered self [1984], 'Present') | |
| A reaction: And so I should hope. Sandel is sort of criticising this view, but it seems obvious that rights of this sort must be basic to any civilised democracy. But how do you decide those rights, if not by a majoritarian decision? |
| 22261 | Liberals say rights always come first, and justice is neutral on social values [Sandel] |
| Full Idea: The liberal claim that the right is prior to the good means that individual rights cannot be sacrificed for the sake of the general good, and that the basic principles of justice cannot be premised on any particular vision of the good life. | |
| From: Michael J. Sandel (Procedural republic and unencumbered self [1984], 'The right') | |
| A reaction: In Rawls, the first thesis is chosen from a neutral position, and the second is all that is needed to affirm rights as basic. These two are the target of Sandel's communitarian claims. Utilitarians will make the sacrifices. No consensus on the good life! |
| 22263 | Liberal justice means the withdrawal of the self, as transcendental or as unencumbered [Sandel] |
| Full Idea: For the liberal concept of justice we must stand to our circumstances always at a certain distance, whether as transcendental subject in the case of Kant, or as unencumbered selves in the case of Rawls. | |
| From: Michael J. Sandel (Procedural republic and unencumbered self [1984], 'Transcendental') | |
| A reaction: Maybe the only way to be unencumbered is to be transcendental. There is an insecure feeling that if the self becomes immanent or encumbered it thereby loses its objective rationality. You wake up one morning and find you are a nazi? |
| 22805 | Liberalism concerns rights, and communitarianism concerns the common good [Sandel, by Avineri/De-Shalit] |
| Full Idea: Sandel argues that liberalism is the politics of rights, while communitarianism is the politics of the common good. | |
| From: report of Michael J. Sandel (Procedural republic and unencumbered self [1984]) by Avineri,S/De-Shalit,A - Intro to 'Communitarianism and Individualism' §4 | |
| A reaction: The first thing on the agenda of the common good should be to assert and protect the rights of individual citizens. How could there be a common good which trampled on individuals? I agree that the common good is prior (e.g. in a pandemic). |