13 ideas
| 10688 | 'Equivocation' is when terms do not mean the same thing in premises and conclusion [Beall/Restall] |
| Full Idea: 'Equivocation' is when the terms do not mean the same thing in the premises and in the conclusion. | |
| From: JC Beall / G Restall (Logical Consequence [2005], Intro) |
| 5637 | Nowadays logic is seen as the science of extensions, not intensions [Scruton] |
| Full Idea: Logicians have come increasingly to realise that logic is the science not of the intension, but of the extension of terms. | |
| From: Roger Scruton (Short History of Modern Philosophy [1981], Ch.4) | |
| A reaction: I take this to be because the notion of a 'set' is basic, which is defined strictly in terms of its members. This move is probably because we can be clear about extensions, but not intensions. Tidiness is no substitute for complex truth. |
| 10690 | Formal logic is invariant under permutations, or devoid of content, or gives the norms for thought [Beall/Restall] |
| Full Idea: Logic is purely formal either when it is invariant under permutation of object (Tarski), or when it has totally abstracted away from all contents, or it is the constitutive norms for thought. | |
| From: JC Beall / G Restall (Logical Consequence [2005], 2) | |
| A reaction: [compressed] The third account sounds rather woolly, and the second one sounds like a tricky operation, but the first one sounds clear and decisive, so I vote for Tarski. |
| 10691 | Logical consequence needs either proofs, or absence of counterexamples [Beall/Restall] |
| Full Idea: Technical work on logical consequence has either focused on proofs, where validity is the existence of a proof of the conclusions from the premises, or on models, which focus on the absence of counterexamples. | |
| From: JC Beall / G Restall (Logical Consequence [2005], 3) |
| 10695 | Logical consequence is either necessary truth preservation, or preservation based on interpretation [Beall/Restall] |
| Full Idea: Two different views of logical consequence are necessary truth-preservation (based on modelling possible worlds; favoured by Realists), or truth-preservation based on the meanings of the logical vocabulary (differing in various models; for Anti-Realists). | |
| From: JC Beall / G Restall (Logical Consequence [2005], 2) | |
| A reaction: Thus Dummett prefers the second view, because the law of excluded middle is optional. My instincts are with the first one. |
| 10689 | A step is a 'material consequence' if we need contents as well as form [Beall/Restall] |
| Full Idea: A logical step is a 'material consequence' and not a formal one, if we need the contents as well as the structure or form. | |
| From: JC Beall / G Restall (Logical Consequence [2005], 2) |
| 10696 | A 'logical truth' (or 'tautology', or 'theorem') follows from empty premises [Beall/Restall] |
| Full Idea: If a conclusion follows from an empty collection of premises, it is true by logic alone, and is a 'logical truth' (sometimes a 'tautology'), or, in the proof-centred approach, 'theorems'. | |
| From: JC Beall / G Restall (Logical Consequence [2005], 4) | |
| A reaction: These truths are written as following from the empty set Φ. They are just implications derived from the axioms and the rules. |
| 10693 | Models are mathematical structures which interpret the non-logical primitives [Beall/Restall] |
| Full Idea: Models are abstract mathematical structures that provide possible interpretations for each of the non-logical primitives in a formal language. | |
| From: JC Beall / G Restall (Logical Consequence [2005], 3) |
| 10692 | Hilbert proofs have simple rules and complex axioms, and natural deduction is the opposite [Beall/Restall] |
| Full Idea: There are many proof-systems, the main being Hilbert proofs (with simple rules and complex axioms), or natural deduction systems (with few axioms and many rules, and the rules constitute the meaning of the connectives). | |
| From: JC Beall / G Restall (Logical Consequence [2005], 3) |
| 14280 | The probability of two events is the first probability times the second probability assuming the first [Bayes] |
| Full Idea: The probability that two events will both happen is the probability of the first [multiplied by] the probability of the second on the supposition that the first happens. | |
| From: Thomas Bayes (Essay on a Problem in the Doctrine of Chances [1763]), quoted by Dorothy Edgington - Conditionals (Stanf) 3.1 |
| 5636 | Cartesian 'ideas' confuse concepts and propositions [Scruton] |
| Full Idea: Cartesian 'ideas' seem to be both concepts and propositions at once. | |
| From: Roger Scruton (Short History of Modern Philosophy [1981], Ch.4) | |
| A reaction: This seems to be the simple reason why modern philosophers don't like this seventeenth century notion. There is something slightly too tidy about the modern notion of propositions built out of concepts. Animals see propositions in a flash. |
| 5660 | Allegiance is prior to the recognition of individual rights [Scruton] |
| Full Idea: Personally I regard allegiance, in the manner of Hegel, as prior to the recognition of individual rights. | |
| From: Roger Scruton (Short History of Modern Philosophy [1981], Bibliog) | |
| A reaction: Scruton notoriously generates rather right-wing views from this basis, but it is also the basis of communitarianism, which can take a softer form. It seems to me self-evident that rights cannot be the prime concept in a society. What society? |
| 5653 | A right is a power which is enforced in the name of justice [Scruton] |
| Full Idea: Rights are enforced in the name of justice, whereas power is enforced come what may. | |
| From: Roger Scruton (Short History of Modern Philosophy [1981], Ch.14) | |
| A reaction: Presumably rights can be claimed as well as enforced, and the notion of a natural right is at least a discussable concept, as in the 'right' of self-defence. Scruton offers us a very right-wing definition of rights. |