15 ideas
| 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. |
| 23295 | Truth cannot be reduced to anything simpler [Davidson] |
| Full Idea: We cannot hope to underpin the concept of truth with something more transparent or easier to grasp. | |
| From: Donald Davidson (The Folly of Trying to Define Truth [1999], p.21) | |
| A reaction: I suppose precise accounts of correspondence or coherence are offered as replacements for truth, but neither of those ever seem to be possible. I agree with accepting truth as a primitive. |
| 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. |
| 23298 | Neither Aristotle nor Tarski introduce the facts needed for a correspondence theory [Davidson] |
| Full Idea: Neither Aristotle's formula nor Tarski's truth definitions are sympathetic to the correspondence theory, because they don't introduce entities like facts or states of affairs for sentences to correspond. | |
| From: Donald Davidson (The Folly of Trying to Define Truth [1999], p.25) | |
| A reaction: This seems convincing, although it is often claimed that both theories offer a sort of correspondence. |
| 23297 | The language to define truth needs a finite vocabulary, to make the definition finite [Davidson] |
| Full Idea: If the definition of the truth predicate is to be finite (Tarski insisted on this), the definition must take advantage of the fact that sentences, though potentially infinite in number, are constructed from a finite vocabulary. | |
| From: Donald Davidson (The Folly of Trying to Define Truth [1999], p.23) | |
| A reaction: Not sure whether this is in the object language or the meta-language, though I guess the former. |
| 23296 | We can elucidate indefinable truth, but showing its relation to other concepts [Davidson] |
| Full Idea: We can still say revealing things about truth, by relating it to other concepts like belief, desire, cause and action. | |
| From: Donald Davidson (The Folly of Trying to Define Truth [1999], p.21) | |
| A reaction: The trickiest concept to link it to is meaning. I think Davidson's view points to the Axiomatic account of truth, which flourished soon after Davidson wrote this. We can give rules for the correct use of 'true'. |
| 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 |
| 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. |
| 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. |
| 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? |
| 3425 | Reduction has been defined as deriving one theory from another by logic and maths [Nagel,E, by Kim] |
| Full Idea: Ernest Nagel defines reduction as the possibility of deriving all laws of one theory by logic and mathematics to another theory, with appropriate 'bridging principles' (either definitions, or empirical laws) connecting the expressions of the two theories. | |
| From: report of Ernest Nagel (The Structure of Science [1961]) by Jaegwon Kim - Philosophy of Mind p.213 | |
| A reaction: This has been labelled as 'weak' reduction, where 'strong' reduction would be identity, as when lightning is reduced to electrical discharge. You reduce x by showing that it is y in disguise. |
| 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? |
| 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. |
| 23294 | It is common to doubt truth when discussing it, but totally accept it when discussing knowledge [Davidson] |
| Full Idea: You are following Plato's lead if you worry about the concept of truth when it is the focus of your attention, but you pretend you understand it when trying to cope with knowledge (or belief, memory, perception etc.). | |
| From: Donald Davidson (The Folly of Trying to Define Truth [1999], p.20) | |
| A reaction: Nice to find someone pointing out this absurdity. He says Hume does the same with doubts about the external world, which he ignores when discussing other minds. Belief is holding true; only truths are actually remembered…. |
| 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. |