Combining Texts

All the ideas for 'The Case for Closure', 'The Unimportance of Identity' and 'Summa totius logicae'

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

21 ideas

2. Reason / B. Laws of Thought / 3. Non-Contradiction
9108 From an impossibility anything follows [William of Ockham]
     Full Idea: From an impossibility anything follows ('quod ex impossibili sequitur quodlibet').
     From: William of Ockham (Summa totius logicae [1323], III.c.xxxvi)
     A reaction: The hallmark of a true logician, I suspect, is that this opinion is really meaningful and important to them. They yearn to follow the logic wherever it leads. Common sense would seem to say that absolutely nothing follows from an impossibility.
2. Reason / E. Argument / 7. Thought Experiments
5515 Imaginary cases are good for revealing our beliefs, rather than the truth [Parfit]
     Full Idea: I believe it is worth considering imaginary cases (such as Teletransportation), as we can use them to discover, not what the truth is, but what we believe.
     From: Derek Parfit (The Unimportance of Identity [1995], p.293)
     A reaction: The trouble is that we might say that IF I were suddenly turned into a pig, then I would come to believe in dualism, but that will not and cannot happen, because dualism is false. It seems essential to accept the natural possibility of the case.
3. Truth / C. Correspondence Truth / 1. Correspondence Truth
9107 A proposition is true if its subject and predicate stand for the same thing [William of Ockham]
     Full Idea: If in the proposition 'This is an angel' subject and predicate stand for the same thing, the proposition is true.
     From: William of Ockham (Summa totius logicae [1323], II.c.ii)
     A reaction: An interesting statement of what looks like a correspondence theory, employing the idea that both the subject and the predicate have a reference. I think Frege would say that 'x is an angel' is unsaturated, and so lacks reference.
3. Truth / G. Axiomatic Truth / 1. Axiomatic Truth
16300 Ockham had an early axiomatic account of truth [William of Ockham, by Halbach]
     Full Idea: Theories structurally very similar to axiomatic compositional theories of truth can be found in Ockham's 'Summa Logicae'.
     From: report of William of Ockham (Summa totius logicae [1323]) by Volker Halbach - Axiomatic Theories of Truth 3
5. Theory of Logic / G. Quantification / 1. Quantification
9106 The word 'every' only signifies when added to a term such as 'man', referring to all men [William of Ockham]
     Full Idea: The syncategorematic word 'every' does not signify any fixed thing, but when added to 'man' it makes the term 'man' stand for all men actually.
     From: William of Ockham (Summa totius logicae [1323], I.c.iv)
     A reaction: Although quantifiers may have become a part of formal logic with Frege, their importance is seen from Aristotle onwards, and it is clearly a key part of William's understanding of logic.
6. Mathematics / C. Sources of Mathematics / 5. Numbers as Adjectival
9113 Just as unity is not a property of a single thing, so numbers are not properties of many things [William of Ockham]
     Full Idea: Number is nothing but the actual numbered things themselves. Hence just as unity is not an accident added to the thing which is one, so number is not an accident of the things which are numbered.
     From: William of Ockham (Summa totius logicae [1323], I.c.xliv)
     A reaction: [William does not necessarily agree with this view] It strikes me as a key point here that any account of the numbers had better work for 'one', though 'zero' might be treated differently. Some people seem to think unity is a property of things.
7. Existence / A. Nature of Existence / 3. Being / g. Particular being
9110 The words 'thing' and 'to be' assert the same idea, as a noun and as a verb [William of Ockham]
     Full Idea: The words 'thing' and 'to be' (esse) signify one and the same thing, but the one in the manner of a noun and the other in the manner of a verb.
     From: William of Ockham (Summa totius logicae [1323], III,II,c,xxvii)
     A reaction: Well said - as you would expect from a thoroughgoing nominalist. I would have thought that this was the last word on the subject of Being, thus rendering any need for me to read Heidegger quite superfluous. Or am I missing something?
7. Existence / C. Structure of Existence / 2. Reduction
5516 Reduction can be by identity, or constitution, or elimination [Parfit, by PG]
     Full Idea: We can distinguish Identifying Reductionism (as in 'persons are bodies'), or Constitutive Reductionism (as in 'persons are distinct, but consist of thoughts etc.'), or Eliminative Reductionism (as in 'there are no persons, only thoughts etc.').
     From: report of Derek Parfit (The Unimportance of Identity [1995], p.295) by PG - Db (ideas)
     A reaction: Constitutive Reductionism seems the most common one, as in 'chemistry just consists of lots of complicated physics'. He doesn't mention bridge laws, which are presumably only required in more complicated cases of constitutive reduction.
8. Modes of Existence / E. Nominalism / 1. Nominalism / b. Nominalism about universals
15388 Universals are single things, and only universal in what they signify [William of Ockham]
     Full Idea: Every universal is one particular thing and it is not a universal except in its signification, in its signifying many thing.
     From: William of Ockham (Summa totius logicae [1323]), quoted by Claude Panaccio - Medieval Problem of Universals 'William'
     A reaction: Sounds as if William might have liked tropes. It seems to leave the problem unanswered (the 'ostrich' problem?). How are they able to signify in this universal way, if each thing is just distinct and particular?
9. Objects / D. Essence of Objects / 6. Essence as Unifier
9109 If essence and existence were two things, one could exist without the other, which is impossible [William of Ockham]
     Full Idea: If essence and existence were two things, then no contradiction would be involved if God preserved the essence of a thing in the world without its existence, or vice versa, its existence without its essence; both of which are impossible.
     From: William of Ockham (Summa totius logicae [1323], III,II,c,xxvii)
     A reaction: Not that William is using the concept of a supreme mind as a tool in argument. His denial of essence as something separable is presumably his denial of the Aristotelian view of universals, as well as of the Platonic view.
11. Knowledge Aims / B. Certain Knowledge / 2. Common Sense Certainty
19553 Commitment to 'I have a hand' only makes sense in a context where it has been doubted [Hawthorne]
     Full Idea: If I utter 'I know I have a hand' then I can only be reckoned a cooperative conversant by my interlocutors on the assumption that there was a real question as to whether I have a hand.
     From: John Hawthorne (The Case for Closure [2005], 2)
     A reaction: This seems to point to the contextualist approach to global scepticism, which concerns whether we are setting the bar high or low for 'knowledge'.
13. Knowledge Criteria / A. Justification Problems / 2. Justification Challenges / c. Knowledge closure
19551 How can we know the heavyweight implications of normal knowledge? Must we distort 'knowledge'? [Hawthorne]
     Full Idea: Those who deny skepticism but accept closure will have to explain how we know the various 'heavyweight' skeptical hypotheses to be false. Do we then twist the concept of knowledge to fit the twin desiderata of closue and anti-skepticism?
     From: John Hawthorne (The Case for Closure [2005], Intro)
     A reaction: [He is giving Dretske's view; Dretske says we do twist knowledge] Thus if I remember yesterday, that has the heavyweight implication that the past is real. Hawthorne nicely summarises why closure produces a philosophical problem.
19552 We wouldn't know the logical implications of our knowledge if small risks added up to big risks [Hawthorne]
     Full Idea: Maybe one cannot know the logical consequences of the proposition that one knows, on account of the fact that small risks add up to big risks.
     From: John Hawthorne (The Case for Closure [2005], 1)
     A reaction: The idea of closure is that the new knowledge has the certainty of logic, and each step is accepted. An array of receding propositions can lose reliability, but that shouldn't apply to logic implications. Assuming monotonic logic, of course.
19554 Denying closure is denying we know P when we know P and Q, which is absurd in simple cases [Hawthorne]
     Full Idea: How could we know that P and Q but not be in a position to know that P (as deniers of closure must say)? If my glass is full of wine, we know 'g is full of wine, and not full of non-wine'. How can we deny that we know it is not full of non-wine?
     From: John Hawthorne (The Case for Closure [2005], 2)
     A reaction: Hawthorne merely raises this doubt. Dretske is concerned with heavyweight implications, but how do you accept lightweight implications like this one, and then suddenly reject them when they become too heavy? [see p.49]
16. Persons / D. Continuity of the Self / 1. Identity and the Self
5514 Psychologists are interested in identity as a type of person, but philosophers study numerical identity [Parfit]
     Full Idea: When psychologists discuss identity, they are typically concerned with the kind of person someone is, or wants to be (as in an 'identity crisis'). But when philosophers discuss identity, it is numerical identity they mean.
     From: Derek Parfit (The Unimportance of Identity [1995], p.293)
     A reaction: I think it is important to note that the philosophical problem breaks down into two areas: whether I have numerical identity with myself over time, and whether other people have it. It may be that two different sets of criteria will emerge.
16. Persons / D. Continuity of the Self / 2. Mental Continuity / b. Self as mental continuity
5521 If my brain-halves are transplanted into two bodies, I have continuity, and don't need identity [Parfit]
     Full Idea: If the two halves of my brain are transplanted into different bodies just like mine, they cannot both be me, since that would make them the same person. ..But my relation to these two contains everything that matters, so identity is not what matters.
     From: Derek Parfit (The Unimportance of Identity [1995], p.314)
     A reaction: I challenge his concept of what 'matters'. He has a rather solipsistic view of the problem, and I take Parfit to be a rather unsociable person, since his friends and partner will be keenly interested in the identities of the new beings.
5522 Over a period of time what matters is not that 'I' persist, but that I have psychological continuity [Parfit]
     Full Idea: We should revise our view about identity over time: what matters isn't that there will be someone alive who will be me; it is rather that there should be at least one living person who will be psychologically continuous with me as I am now.
     From: Derek Parfit (The Unimportance of Identity [1995], p.316)
     A reaction: Parfit and Locke seem to agree on this, and it is no accident that they both like 'science fiction' examples. Apparently Parfit wouldn't bat an eyelid if someone threatened to cut his corpus callosum. I rate it as a catastrophe for my current existence.
16. Persons / D. Continuity of the Self / 4. Split Consciousness
5519 It is fine to save two dying twins by merging parts of their bodies into one, and identity is irrelevant [Parfit]
     Full Idea: If I am largely paralysed, and my twin brother is dying of brain disease, then if the operation to graft my head onto his body is offered, I should accept the operation, and it is irrelevant whether this person would be me.
     From: Derek Parfit (The Unimportance of Identity [1995], p.308)
     A reaction: Parfit notes that the brain is a particularly significant part of the process. The fact that I might cheerfully accept this offer without philosophical worries doesn't get rid of the question 'who is this person?' Who should they remain married to?
5520 If two humans are merged surgically, the new identity is a purely verbal problem [Parfit]
     Full Idea: If there is someone with my head and my brother's body, it is a merely verbal question whether that person will be me, and that is why, even if it won't be me, that doesn't matter. ..What matters is not identity, but the facts of which identity consists.
     From: Derek Parfit (The Unimportance of Identity [1995], p.310)
     A reaction: It strikes me that from the subjective psychological point of view identity is of little interest, but from the objective external viewpoint (e.g. the forensic one) such questions are highly significant, and rightly so.
16. Persons / E. Rejecting the Self / 4. Denial of the Self
5518 It doesn't matter whether I exist with half my components replaced (any more than an audio system) [Parfit]
     Full Idea: It is quite uninteresting whether, with half its components replaced, I have the same audio system, and also whether I exist if half of my body were simultaneously replaced.
     From: Derek Parfit (The Unimportance of Identity [1995], p.302)
     A reaction: It is impossible to deny this, if the part replaced is not the brain. My doubt about Parfit's thesis is that while I may not care whether some modified thing is still me, my lawyers and the police might be very concerned.
19. Language / D. Propositions / 4. Mental Propositions
9105 Some concepts for propositions exist only in the mind, and in no language [William of Ockham]
     Full Idea: Conceptual terms and the propositions formed by them are those mental words which do not belong to any language; they remain only in the mind and cannot be uttered exteriorly, though signs subordinated to these can be exteriorly uttered.
     From: William of Ockham (Summa totius logicae [1323], I.c.i)
     A reaction: [He cites Augustine] A glimmer of the idea of Mentalese, and is probably an integral part of any commitment to propositions. Quine would hate it, but I like it. Logicians seem to dislike anything that cannot be articulated, but brains are like that.