Combining Texts

All the ideas for 'works', 'talk' and 'Logical Necessity'

unexpand these ideas     |    start again     |     specify just one area for these texts


29 ideas

1. Philosophy / D. Nature of Philosophy / 1. Philosophy
He studied philosophy by suspending his judgement on everything [Pyrrho, by Diog. Laertius]
     Full Idea: He studied philosophy on the principle of suspending his judgement on all points.
     From: report of Pyrrho (reports [c.325 BCE]) by Diogenes Laertius - Lives of Eminent Philosophers 09.Py.3
     A reaction: In what sense was Pyrrho a philosopher, then? He must have asserted SOME generalised judgments.
2. Reason / A. Nature of Reason / 9. Limits of Reason
Sceptics say reason is only an instrument, because reason can only be attacked with reason [Pyrrho, by Diog. Laertius]
     Full Idea: The Sceptics say that they only employ reason as an instrument, because it is impossible to overturn the authority of reason, without employing reason.
     From: report of Pyrrho (reports [c.325 BCE]) by Diogenes Laertius - Lives of Eminent Philosophers 09.Py.8
4. Formal Logic / D. Modal Logic ML / 3. Modal Logic Systems / h. System S5
The logic of metaphysical necessity is S5 [Rumfitt]
     Full Idea: It is a widely accepted thesis that the logic of metaphysical necessity is S5.
     From: Ian Rumfitt (Logical Necessity [2010], §5)
     A reaction: Rumfitt goes on to defend this standard view (against Dummett's defence of S4). The point, I take it, is that one can only assert that something is 'true in all possible worlds' only when the worlds are all accessible to one another.
5. Theory of Logic / B. Logical Consequence / 1. Logical Consequence
Soundness in argument varies with context, and may be achieved very informally indeed [Rumfitt]
     Full Idea: Our ordinary standards for deeming arguments to be sound vary greatly from context to context. Even the package tourist's syllogism ('It's Tuesday, so this is Belgium') may meet the operative standards for soundness.
     From: Ian Rumfitt (Logical Necessity [2010], Intro)
     A reaction: No doubt one could spell out the preconceptions of package tourist reasoning, and arrive at the logical form of the implication which is being offered.
There is a modal element in consequence, in assessing reasoning from suppositions [Rumfitt]
     Full Idea: There is a modal element in consequence, in its applicability to assessing reasoning from suppositions.
     From: Ian Rumfitt (Logical Necessity [2010], §2)
We reject deductions by bad consequence, so logical consequence can't be deduction [Rumfitt]
     Full Idea: A rule is to be rejected if it enables us to deduce from some premisses a purported conclusion that does not follow from them in the broad sense. The idea that deductions answer to consequence is incomprehensible if consequence consists in deducibility.
     From: Ian Rumfitt (Logical Necessity [2010], §2)
5. Theory of Logic / D. Assumptions for Logic / 3. Contradiction
Contradictions include 'This is red and not coloured', as well as the formal 'B and not-B' [Rumfitt]
     Full Idea: Overt contradictions include formal contradictions of form 'B and not B', but I also take them to include 'This is red all over and green all over' and 'This is red and not coloured'.
     From: Ian Rumfitt (Logical Necessity [2010], Intro)
5. Theory of Logic / H. Proof Systems / 2. Axiomatic Proof
Geometrical axioms in logic are nowadays replaced by inference rules (which imply the logical truths) [Rumfitt]
     Full Idea: The geometrical style of formalization of logic is now little more than a quaint anachronism, largely because it fails to show logical truths for what they are: simply by-products of rules of inference that are applicable to suppositions.
     From: Ian Rumfitt (Logical Necessity [2010], §1)
     A reaction: This is the rejection of Russell-style axiom systems in favour of Gentzen-style natural deduction systems (starting from rules). Rumfitt quotes Dummett in support.
9. Objects / C. Structure of Objects / 6. Constitution of an Object
If someone squashed a horse to make a dog, something new would now exist [Mnesarchus]
     Full Idea: If, for the sake of argument, someone were to mould a horse, squash it, then make a dog, it would be reasonable for us on seeing this to say that this previously did not exist but now does exist.
     From: Mnesarchus (fragments/reports [c.120 BCE]), quoted by John Stobaeus - Anthology 179.11
     A reaction: Locke would say it is new, because the substance is the same, but a new life now exists. A sword could cease to exist and become a new ploughshare, I would think. Apply this to the Ship of Theseus. Is form more important than substance?
10. Modality / A. Necessity / 3. Types of Necessity
A distinctive type of necessity is found in logical consequence [Rumfitt, by Hale/Hoffmann,A]
     Full Idea: Rumfitt argues that there is a distinctive notion of necessity implicated in the notion of logical consequence.
     From: report of Ian Rumfitt (Logical Necessity [2010]) by Bob Hale/ Aviv Hoffmann - Introduction to 'Modality' 2
10. Modality / A. Necessity / 6. Logical Necessity
Logical necessity is when 'necessarily A' implies 'not-A is contradictory' [Rumfitt]
     Full Idea: By the notion of 'logical necessity' I mean that there is a sense of 'necessary' for which 'It is necessary that A' implies and is implied by 'It is logically contradictory that not A'. ...From this, logical necessity is implicated in logical consequence.
     From: Ian Rumfitt (Logical Necessity [2010], Intro)
     A reaction: Rumfitt expresses a commitment to classical logic at this point. We will need to be quite sure what we mean by 'contradiction', which will need a clear notion of 'truth'....
A logically necessary statement need not be a priori, as it could be unknowable [Rumfitt]
     Full Idea: There is no reason to suppose that any statement that is logically necessary (in the present sense) is knowable a priori. ..If a statement is logically necessary, its negation will yield a contradiction, but that does not imply that someone could know it.
     From: Ian Rumfitt (Logical Necessity [2010], §2)
     A reaction: This remark is aimed at Dorothy Edgington, who holds the opposite view. Rumfitt largely defends McFetridge's view (q.v.).
Narrow non-modal logical necessity may be metaphysical, but real logical necessity is not [Rumfitt]
     Full Idea: While Fine suggests defining a narrow notion of logical necessity in terms of metaphysical necessity by 'restriction' (to logical truths that can be defined in non-modal terms), this seems unpromising for broad logical necessity, which is modal.
     From: Ian Rumfitt (Logical Necessity [2010], §2)
     A reaction: [compressed] He cites Kit Fine 2002. Rumfitt glosses the non-modal definitions as purely formal. The metaphysics lurks somewhere in the proof.
10. Modality / E. Possible worlds / 1. Possible Worlds / e. Against possible worlds
If a world is a fully determinate way things could have been, can anyone consider such a thing? [Rumfitt]
     Full Idea: A world is usually taken to be a fully determinate way that things could have been; but then one might seriously wonder whether anyone is capable of 'considering' such a thing at all.
     From: Ian Rumfitt (Logical Necessity [2010], §4)
     A reaction: This has always worried me. If I say 'maybe my coat is in the car', I would hate to think that I had to be contemplating some entire possible world (including all the implications of my coat not being on the hat stand).
13. Knowledge Criteria / A. Justification Problems / 1. Justification / a. Justification issues
If we need a criterion of truth, we need to know whether it is the correct criterion [Pyrrho, by Fogelin]
     Full Idea: Against the Stoics, the Pyrrhonians argued that if someone presents a criterion of truth, then it will be important to determine whether it is the correct criterion.
     From: report of Pyrrho (reports [c.325 BCE]) by Robert Fogelin - Walking the Tightrope of Reason Ch.4
     A reaction: Hence Davidson says that attempts to define truth are 'folly'. If something has to be taken as basic, then truth seems a good candidate (since, for example, logical operators could not otherwise be defined by means of 'truth' tables).
13. Knowledge Criteria / D. Scepticism / 1. Scepticism
The Pyrrhonians attacked the dogmas of professors, not ordinary people [Pyrrho, by Fogelin]
     Full Idea: The attacks of the Pyrrhonian sceptics are directed against the dogmas of the 'professors', not against the beliefs of the common people pursuing the business of daily life.
     From: report of Pyrrho (reports [c.325 BCE]) by Robert Fogelin - Walking the Tightrope of Reason Ch.4
     A reaction: This may be because they thought that ordinary people were too confused to be worth attacking, rather than because they lived in a state of beautifully appropriate beliefs. Naïve realism is certainly worth attacking.
13. Knowledge Criteria / D. Scepticism / 6. Scepticism Critique
Academics said that Pyrrhonians were guilty of 'negative dogmatism' [Pyrrho, by Fogelin]
     Full Idea: The ancient Academic sceptics charged the Pyrrhonian sceptics with 'negative dogmatism' when they claimed that a certain kind of knowledge is impossible.
     From: report of Pyrrho (reports [c.325 BCE]) by Robert Fogelin - Walking the Tightrope of Reason Ch.4
     A reaction: It is this kind of point which should push us towards some sort of rationalism, because certain a priori 'dogmas' seem to be indispensable to get any sort of discussion off the ground. The only safe person is Cratylus (see Idea 578).
13. Knowledge Criteria / E. Relativism / 1. Relativism
Individuals vary in responses and feelings (Mode 2) [Pyrrho, by Diog. Laertius]
     Full Idea: Second mode: individual men vary in responses and feelings (heat and cold, for example).
     From: report of Pyrrho (reports [c.325 BCE]) by Diogenes Laertius - Lives of Eminent Philosophers 09.Py.9
Animals vary in their feelings and judgements (Mode 1) [Pyrrho, by Diog. Laertius]
     Full Idea: First mode: animals vary in their feelings and judgements (of food, for example).
     From: report of Pyrrho (reports [c.325 BCE]) by Diogenes Laertius - Lives of Eminent Philosophers 09.Py.9
Perception varies with madness or disease (Mode 4) [Pyrrho, by Diog. Laertius]
     Full Idea: Fourth mode: perceivers vary in their mental and physical state (such as the mad and the sick).
     From: report of Pyrrho (reports [c.325 BCE]) by Diogenes Laertius - Lives of Eminent Philosophers 09.Py.9
Perception is affected by expectations (Mode 9) [Pyrrho, by Diog. Laertius]
     Full Idea: Ninth mode: we perceive things according to what we expect (earthquakes and sunshine).
     From: report of Pyrrho (reports [c.325 BCE]) by Diogenes Laertius - Lives of Eminent Philosophers 09.Py.9
Perception of things depends on their size or quantity (Mode 8) [Pyrrho, by Diog. Laertius]
     Full Idea: Eighth mode: perceptions of things depend on their magnitude or quantity (food and wine).
     From: report of Pyrrho (reports [c.325 BCE]) by Diogenes Laertius - Lives of Eminent Philosophers 09.Py.9
Perception of objects depends on surrounding conditions (Mode 6) [Pyrrho, by Diog. Laertius]
     Full Idea: Sixth mode: the perception of an object depends on surrounding conditions (sunlight and lamplight).
     From: report of Pyrrho (reports [c.325 BCE]) by Diogenes Laertius - Lives of Eminent Philosophers 09.Py.9
Objects vary according to which sense perceives them (Mode 3) [Pyrrho, by Diog. Laertius]
     Full Idea: Third mode: things like an apple vary according to which sense perceives them (yellow, sweet, and fragrant).
     From: report of Pyrrho (reports [c.325 BCE]) by Diogenes Laertius - Lives of Eminent Philosophers 09.Py.9
Judgements vary according to local culture and law (Mode 5) [Pyrrho, by Diog. Laertius]
     Full Idea: Fifth mode: judgements vary according to local custom, law and culture (Persians marry their daughters).
     From: report of Pyrrho (reports [c.325 BCE]) by Diogenes Laertius - Lives of Eminent Philosophers 09.Py.9
Perception varies with viewing distance and angle (Mode 7) [Pyrrho, by Diog. Laertius]
     Full Idea: Seventh mode: perception varies according to viewing distance and angle (the sun, and a dove's neck).
     From: report of Pyrrho (reports [c.325 BCE]) by Diogenes Laertius - Lives of Eminent Philosophers 09.Py.9
Perception and judgement depend on comparison (Mode 10) [Pyrrho, by Diog. Laertius]
     Full Idea: Tenth mode: perceptions and judgements depend on comparison (light/heavy, above/below).
     From: report of Pyrrho (reports [c.325 BCE]) by Diogenes Laertius - Lives of Eminent Philosophers 09.Py.9
26. Natural Theory / C. Causation / 7. Eliminating causation
There are no causes, because they are relative, and alike things can't cause one another [Pyrrho, by Diog. Laertius]
     Full Idea: The idea of cause is relative to that of which it is the cause, and so has no real existence. …Also cause must either be body causing body, or incorporeal causing incorporeal, and neither of these is possible.
     From: report of Pyrrho (reports [c.325 BCE]) by Diogenes Laertius - Lives of Eminent Philosophers 09.11.11
27. Natural Reality / A. Classical Physics / 1. Mechanics / a. Explaining movement
Motion can't move where it is, and can't move where it isn't, so it can't exist [Pyrrho, by Diog. Laertius]
     Full Idea: Motion is not moved in the place in which it is is, and it is impossible that it should be moved in the place in which it is not, so there is no such thing as motion.
     From: report of Pyrrho (reports [c.325 BCE]) by Diogenes Laertius - Lives of Eminent Philosophers 09.11.11