14 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) |
| 9987 | An aggregate in which order does not matter I call a 'set' [Bolzano] |
| Full Idea: An aggregate whose basic conception renders the arrangement of its members a matter of indifference, and whose permutation therefore produces no essential difference, I call a 'set'. | |
| From: Bernard Bolzano (Paradoxes of the Infinite [1846], §4), quoted by William W. Tait - Frege versus Cantor and Dedekind IX | |
| A reaction: The idea of 'sets' was emerging before Cantor formalised it, and clarified it by thinking about infinite sets. Nowadays we also have 'ordered' sets, which rather contradicts Bolzano, and we also expect the cardinality to be determinate. |
| 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) |
| 10856 | A truly infinite quantity does not need to be a variable [Bolzano] |
| Full Idea: A truly infinite quantity (for example, the length of a straight line, unbounded in either direction) does not by any means need to be a variable. | |
| From: Bernard Bolzano (Paradoxes of the Infinite [1846]), quoted by Brian Clegg - Infinity: Quest to Think the Unthinkable §10 | |
| A reaction: This is an important idea, followed up by Cantor, which relegated to the sidelines the view of infinity as simply something that could increase without limit. Personally I like the old view, but there is something mathematically stable about infinity. |
| 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) |
| 19520 | Evidentialism is not axiomatic; the evidence itself inclines us towards evidentialism [Conee] |
| Full Idea: Evidentialism does not support beginning epistemology by taking for granted that evidentialism is true. ...Rather, what potentially justifies belief in intial epistemic data and initial procedures of inquiry is the evidence itself. | |
| From: Earl Conee (First Things First [2004], 'Getting') | |
| A reaction: This sounds good. I much prefer talk of 'evidence' to talk of 'perceptions', because evidence has been licked into shape, and its significance has been clarified. That is the first step towards the coherence we seek. |
| 19521 | If pure guesses were reliable, reliabilists would have to endorse them [Conee] |
| Full Idea: Reliabilism would count pure guesses as good reasons if guessing were properly reliable. | |
| From: Earl Conee (First Things First [2004], 'Getting') | |
| A reaction: See D.H. Lawrence's short story 'The Rocking Horse Winner'. This objection strikes me as being so devastating that it is almost conclusive. Except that pure guesses are never ever reliable, over a decent period of time. |
| 19522 | More than actual reliability is needed, since I may mistakenly doubt what is reliable [Conee] |
| Full Idea: Sheer reliability does not justify belief. ...It may be, for instance, that we have strong though misleading reason to deny the method's reliability. | |
| From: Earl Conee (First Things First [2004], 'Circles') | |
| A reaction: That is, we accept a justification if we judge the method to be reliable, not if it IS reliable. I can disbelieve all the reliable information that arrives in my mind. People do that all the time! Hatred of experts! Support for internalism? |
| 19523 | Reliabilism is poor on reflective judgements about hypothetical cases [Conee] |
| Full Idea: An unrefined reliability theory does a poor job at capturing reflective judgements about hypothetical cases | |
| From: Earl Conee (First Things First [2004], 'Stroud's') | |
| A reaction: Reliability can only be a test for tried and tested ways. No one can say whether imagining a range of possibilities is reliable or not. Is prediction a reliable route to knowledge? |