19 ideas
| 18755 | Validity is explained as truth in all models, because that relies on the logical terms [McGee] |
| Full Idea: A model of a language assigns values to non-logical terms. If a sentence is true in every model, its truth doesn't depend on those non-logical terms. Hence the validity of an argument comes from its logical form. Thus models explain logical validity. | |
| From: Vann McGee (Logical Consequence [2014], 4) | |
| A reaction: [compressed] Thus you get a rigorous account of logical validity by only allowing the rigorous input of model theory. This is the modern strategy of analytic philosophy. But is 'it's red so it's coloured' logically valid? |
| 18751 | Natural language includes connectives like 'because' which are not truth-functional [McGee] |
| Full Idea: Natural language includes connectives that are not truth-functional. In order for 'p because q' to be true, both p and q have to be true, but knowing the simpler sentences are true doesn't determine whether the larger sentence is true. | |
| From: Vann McGee (Logical Consequence [2014], 2) |
| 18761 | Second-order variables need to range over more than collections of first-order objects [McGee] |
| Full Idea: To get any advantage from moving to second-order logic, we need to assign to second-order variables a role different from merely ranging over collections made up of things the first-order variables range over. | |
| From: Vann McGee (Logical Consequence [2014], 7) | |
| A reaction: Thus it is exciting if they range over genuine properties, but not so exciting if you merely characterise those properties as sets of first-order objects. This idea leads into a discussion of plural quantification. |
| 18753 | An ontologically secure semantics for predicate calculus relies on sets [McGee] |
| Full Idea: We can get a less ontologically perilous presentation of the semantics of the predicate calculus by using sets instead of concepts. | |
| From: Vann McGee (Logical Consequence [2014], 4) | |
| A reaction: The perilous versions rely on Fregean concepts, and notably Russell's 'concept that does not fall under itself'. The sets, of course, have to be ontologically secure, and so will involve the iterative conception, rather than naive set theory. |
| 18754 | Logically valid sentences are analytic truths which are just true because of their logical words [McGee] |
| Full Idea: Logically valid sentences are a species of analytic sentence, being true not just in virtue of the meanings of their words, but true in virtue of the meanings of their logical words. | |
| From: Vann McGee (Logical Consequence [2014], 4) | |
| A reaction: A helpful link between logical truths and analytic truths, which had not struck me before. |
| 18757 | Soundness theorems are uninformative, because they rely on soundness in their proofs [McGee] |
| Full Idea: Soundness theorems are seldom very informative, since typically we use informally, in proving the theorem, the very same rules whose soundness we are attempting to establish. | |
| From: Vann McGee (Logical Consequence [2014], 5) | |
| A reaction: [He cites Quine 1935] |
| 18760 | The culmination of Euclidean geometry was axioms that made all models isomorphic [McGee] |
| Full Idea: One of the culminating achievements of Euclidean geometry was categorical axiomatisations, that describe the geometric structure so completely that any two models of the axioms are isomorphic. The axioms are second-order. | |
| From: Vann McGee (Logical Consequence [2014], 7) | |
| A reaction: [He cites Veblen 1904 and Hilbert 1903] For most mathematicians, categorical axiomatisation is the best you can ever dream of (rather than a single true axiomatisation). |
| 18439 | Because things can share attributes, we cannot individuate attributes clearly [Quine] |
| Full Idea: No two classes have exactly the same members, but two different attributes may be attributes of exactly the same things. Classes are identical when their members are identical. ...On the other hand, attributes have no clear principle of individuation. | |
| From: Willard Quine (On the Individuation of Attributes [1975], p.100) |
| 18442 | You only know an attribute if you know what things have it [Quine] |
| Full Idea: May we not say that you know an attribute only insofar as you know what things have it? | |
| From: Willard Quine (On the Individuation of Attributes [1975], p.106) | |
| A reaction: Simple, and the best defence of class nominalism (a very implausible theory) which I have encountered. Do I have to know all the things? Do I not know 'red' if I don't know tomatoes have it? |
| 18441 | No entity without identity (which requires a principle of individuation) [Quine] |
| Full Idea: We have an acceptable notion of class, or physical object, or attribute, or any other sort of object, only insofar as we have an acceptable principle of individuation for that sort of object. There is no entity without identity. | |
| From: Willard Quine (On the Individuation of Attributes [1975], p.102) | |
| A reaction: Note that this is his criterion for an 'acceptable' notion. Presumably that is for science. It permits less acceptable notions which don't come up to the standard. And presumably true things can be said about the less acceptable entities. |
| 18440 | Identity of physical objects is just being coextensive [Quine] |
| Full Idea: Physical objects are identical if and only if coextensive. | |
| From: Willard Quine (On the Individuation of Attributes [1975], p.101) | |
| A reaction: The supposed counterexample to this is the statue and the clay it is made of, which are said to have different modal properties (destroying the statue doesn't destroy the clay). |
| 3654 | The pineal gland links soul to body, and unites the two symmetrical sides of the body [Descartes, by PG] |
| Full Idea: The soul is united with the body in just one place, a gland (the pineal) in the centre of the brain. It is placed so that its slightest movement will affect the passions, and it plays the essential role of uniting the two symmetrical sides of the body. | |
| From: report of René Descartes (The Passions of the Soul [1649], §31) by PG - Db (ideas) | |
| A reaction: See Idea 4862 for Spinoza's nice response to Descartes' proposal. If Descartes had followed brain research for the last four hundred years, at what point would he have wavered? If every single part of the brain seems to 'interact', dualism looks unlikely. |
| 4015 | For Descartes passions are God-given preservers of the mind-body union [Descartes, by Taylor,C] |
| Full Idea: Descartes sees passions not as opinions, but as functional devices that the Creator has designed for us to help preserve the body-soul substantial union. | |
| From: report of René Descartes (The Passions of the Soul [1649]) by Charles Taylor - Sources of the Self §8 | |
| A reaction: I wonder what Descartes would have made of the theory of evolution? |
| 4313 | Are there a few primary passions (say, joy, sadness and desire)? [Descartes, by Cottingham] |
| Full Idea: Descartes says there are six primary passions (wonder, love, hatred, desire, joy and sadness); Spinoza says there are just three (joy, sadness and desire). | |
| From: report of René Descartes (The Passions of the Soul [1649]) by John Cottingham - The Rationalists p.172 | |
| A reaction: A dubious project. However, it is now agreed that there are a few (six?) basic universal facial expressions, to which these passions may correspond. |
| 23989 | There are six primitive passions: wonder, love, hatred, desire, joy and sadness [Descartes, by Goldie] |
| Full Idea: Descartes said there are six primitive passions, namely wonder, love, hatred, desire, joy and sadness. The others are either species of these, or composed of them. | |
| From: report of René Descartes (The Passions of the Soul [1649], 353) by Peter Goldie - The Emotions 4 'Evidence' | |
| A reaction: [not sure about ref] It's a nice touch to add 'wonder', which doesn't make it onto anyone else's list. |
| 18762 | A maxim claims that if we are allowed to assert a sentence, that means it must be true [McGee] |
| Full Idea: If our linguistic conventions entitle us to assert a sentence, they thereby make it true, because of the maxim that 'truth is the norm of assertion'. | |
| From: Vann McGee (Logical Consequence [2014], 8) | |
| A reaction: You could only really deny that maxim if you had no belief at all in truth, but then you can assert anything you like (with full entitlement). Maybe you can assert anything you like as long as it doesn't upset anyone? Etc. |
| 20037 | Merely willing to walk leads to our walking [Descartes] |
| Full Idea: Our merely willing to walk has the consequence that our legs move and we walk. | |
| From: René Descartes (The Passions of the Soul [1649], 18), quoted by Rowland Stout - Action 1 'Volitionism' | |
| A reaction: Stout attributes this to Descartes' dualism, as if legs are separate from persons. Stout says the idea of a prior mental act is not usually now considered as part of an action, or even to exist at all. If the volition is intentional, there is a regress. |
| 16763 | We don't die because the soul departs; the soul departs because the organs cease functioning [Descartes] |
| Full Idea: We ought to hold, on the contrary, that the soul takes its leave when we die only because this heat ceases and the organs that bring about bodily movement decay. | |
| From: René Descartes (The Passions of the Soul [1649], I.5), quoted by Robert Pasnau - Metaphysical Themes 1274-1671 24.5 | |
| A reaction: This sounds like a pretty major change in our concept of death, given that we all now agree with Descartes. |
| 4016 | Descartes makes strength of will the central virtue [Descartes, by Taylor,C] |
| Full Idea: Descartes makes strength of will the central virtue. | |
| From: report of René Descartes (The Passions of the Soul [1649]) by Charles Taylor - Sources of the Self §8 | |
| A reaction: Presumably strength of will can serve evil ends, so this is a bit confusing. |