Combining Texts

All the ideas for 'Substance and Individuation in Leibniz', 'On Second-Order Logic' and 'Darwin's Dangerous Idea'

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20 ideas

5. Theory of Logic / A. Overview of Logic / 7. Second-Order Logic

14249	Boolos reinterprets second-order logic as plural logic [Boolos, by Oliver/Smiley]
	Full Idea: Boolos's conception of plural logic is as a reinterpretation of second-order logic.
	From: report of George Boolos (On Second-Order Logic [1975]) by Oliver,A/Smiley,T - What are Sets and What are they For? n5
	A reaction: Oliver and Smiley don't accept this view, and champion plural reference differently (as, I think, some kind of metalinguistic device?).

10830	Second-order logic metatheory is set-theoretic, and second-order validity has set-theoretic problems [Boolos]
	Full Idea: The metatheory of second-order logic is hopelessly set-theoretic, and the notion of second-order validity possesses many if not all of the epistemic debilities of the notion of set-theoretic truth.
	From: George Boolos (On Second-Order Logic [1975], p.45)
	A reaction: Epistemic problems arise when a logic is incomplete, because some of the so-called truths cannot be proved, and hence may be unreachable. This idea indicates Boolos's motivation for developing a theory of plural quantification.

5. Theory of Logic / C. Ontology of Logic / 1. Ontology of Logic

10829	A sentence can't be a truth of logic if it asserts the existence of certain sets [Boolos]
	Full Idea: One may be of the opinion that no sentence ought to be considered as a truth of logic if, no matter how it is interpreted, it asserts that there are sets of certain sorts.
	From: George Boolos (On Second-Order Logic [1975], p.44)
	A reaction: My intuition is that in no way should any proper logic assert the existence of anything at all. Presumably interpretations can assert the existence of numbers or sets, but we should be able to identify something which is 'pure' logic. Natural deduction?

5. Theory of Logic / G. Quantification / 2. Domain of Quantification

10832	'∀x x=x' only means 'everything is identical to itself' if the range of 'everything' is fixed [Boolos]
	Full Idea: One may say that '∀x x=x' means 'everything is identical to itself', but one must realise that one's answer has a determinate sense only if the reference (range) of 'everything' is fixed.
	From: George Boolos (On Second-Order Logic [1975], p.46)
	A reaction: This is the problem now discussed in the recent book 'Absolute Generality', of whether one can quantify without specifying a fixed or limited domain.

5. Theory of Logic / K. Features of Logics / 4. Completeness

10834	Weak completeness: if it is valid, it is provable. Strong: it is provable from a set of sentences [Boolos]
	Full Idea: A weak completeness theorem shows that a sentence is provable whenever it is valid; a strong theorem, that a sentence is provable from a set of sentences whenever it is a logical consequence of the set.
	From: George Boolos (On Second-Order Logic [1975], p.52)
	A reaction: So the weak version says |- φ → |= φ, and the strong versions says Γ |- φ → Γ |= φ. Presumably it is stronger if it can specify the source of the inference.

5. Theory of Logic / K. Features of Logics / 6. Compactness

13841	Why should compactness be definitive of logic? [Boolos, by Hacking]
	Full Idea: Boolos asks why on earth compactness, whatever its virtues, should be definitive of logic itself.
	From: report of George Boolos (On Second-Order Logic [1975]) by Ian Hacking - What is Logic? §13

6. Mathematics / B. Foundations for Mathematics / 4. Axioms for Number / e. Peano arithmetic 2nd-order

10833	Many concepts can only be expressed by second-order logic [Boolos]
	Full Idea: The notions of infinity and countability can be characterized by second-order sentences, though not by first-order sentences (as compactness and Skolem-Löwenheim theorems show), .. as well as well-ordering, progression, ancestral and identity.
	From: George Boolos (On Second-Order Logic [1975], p.48)

8. Modes of Existence / A. Relations / 1. Nature of Relations

13076	Scholastics treat relations as two separate predicates of the relata [Cover/O'Leary-Hawthorne]
	Full Idea: The scholastics treated it as a step in the right explanatory direction to analyze a relational statement of the form 'aRb' into two subject-predicate statements, attributing different relational predicates to a and to b.
	From: Cover,J/O'Leary-Hawthorne,J (Substance and Individuation in Leibniz [1999], 2.2.1)
	A reaction: The only alternative seems to be Russell's view of relations as pure universals, having a life of their own, quite apart from their relata. Or you could take them as properties of space, time (and powers?), external to the relata?

9. Objects / A. Existence of Objects / 5. Individuation / a. Individuation

13102	If you individuate things by their origin, you still have to individuate the origins themselves [Cover/O'Leary-Hawthorne]
	Full Idea: If we go for the necessity-of-origins view, A and B are different if the origin of A is different from the origin of B. But one is left with the further question 'When is the origin of A distinct from the origin of B?'
	From: Cover,J/O'Leary-Hawthorne,J (Substance and Individuation in Leibniz [1999], 7.4.1)
	A reaction: There may be an answer to this, in a regress of origins that support one another, but in the end the objection is obviously good. You can't begin to refer to an 'origin' if you can't identify anything in the first place.

13103	Numerical difference is a symmetrical notion, unlike proper individuation [Cover/O'Leary-Hawthorne]
	Full Idea: Scholastics distinguished criteria of numerical difference from questions of individuation proper, since numerical difference is a symmetrical notion.
	From: Cover,J/O'Leary-Hawthorne,J (Substance and Individuation in Leibniz [1999], 7.4.1)
	A reaction: This apparently old-fashioned point appears to be conclusively correct. Modern thinkers, though, aren't comfortable with proper individuation, because they don't believe in concepts like 'essence' and 'substance' that are needed for the job.

9. Objects / A. Existence of Objects / 5. Individuation / d. Individuation by haecceity

13104	Haecceity as property, or as colourless thisness, or as singleton set [Cover/O'Leary-Hawthorne]
	Full Idea: There is a contemporary property construal of haecceities, ...and a Scotistic construal as primitive, 'colourless' thisnesses which, unlike singleton-set haecceities, are aimed to do some explanatory work.
	From: Cover,J/O'Leary-Hawthorne,J (Substance and Individuation in Leibniz [1999], 7.4.4)
	A reaction: [He associates the contemporary account with David Kaplan] I suppose I would say that individuation is done by properties, but not by some single property, so I take it that I don't believe in haecceities at all. What individuates a haecceity?

9. Objects / B. Unity of Objects / 2. Substance / a. Substance

13100	Maybe 'substance' is more of a mass-noun than a count-noun [Cover/O'Leary-Hawthorne]
	Full Idea: We could think of 'substance' on the model of a mass noun, rather than a count noun.
	From: Cover,J/O'Leary-Hawthorne,J (Substance and Individuation in Leibniz [1999], 7.3)
	A reaction: They offer this to help Leibniz out of a mess, but I think he would be appalled. The proposal seems close to 'prime matter' in Aristotle, which never quite does the job required of it. The idea is nice, though, and should be taken seriously.

9. Objects / B. Unity of Objects / 2. Substance / c. Types of substance

13068	We can ask for the nature of substance, about type of substance, and about individual substances [Cover/O'Leary-Hawthorne]
	Full Idea: In the 'blueprint' approach to substance, we confront at least three questions: What is it for a thing to be an individual substance? What is it for a thing to be the kind of substance that it is? What is it to be that very individual substance?
	From: Cover,J/O'Leary-Hawthorne,J (Substance and Individuation in Leibniz [1999], 1.1.1)
	A reaction: My working view is that the answer to the first question is that substance is essence, that the second question is overrated and parasitic on the third, and that the third is the key question, and also reduces to essence.

9. Objects / B. Unity of Objects / 2. Substance / d. Substance defined

13069	The general assumption is that substances cannot possibly be non-substances [Cover/O'Leary-Hawthorne]
	Full Idea: There is a widespread assumption, now and in the past, that substances are essentially substances: nothing is actually a substance but possibly a non-substance.
	From: Cover,J/O'Leary-Hawthorne,J (Substance and Individuation in Leibniz [1999], 1.1.2)
	A reaction: It seems to me that they clearly mean, in this context, that substances are 'necessarily' substances, not that they are 'essentially' substances. I would just say that substances are essences, and leave the necessity question open.

9. Objects / D. Essence of Objects / 7. Essence and Necessity / a. Essence as necessary properties

13072	Modern essences are sets of essential predicate-functions [Cover/O'Leary-Hawthorne]
	Full Idea: The modern view of essence is that the essence of a particular thing is given by the set of predicate-functions essential to it, and the essence of any kind is given by the set of predicate-functions essential to every possible member of that kind.
	From: Cover,J/O'Leary-Hawthorne,J (Substance and Individuation in Leibniz [1999], 1.2.2)
	A reaction: Thus the modern view has elided the meanings of 'essential' and 'necessary' when talking of properties. They are said to be 'functions' from possible worlds to individuals. The old view (and mine) demands real essences, not necessary properties.

17080	Modern essentialists express essence as functions from worlds to extensions for predicates [Cover/O'Leary-Hawthorne]
	Full Idea: The modern essentialist gives the same metaphysical treatment to every grammatical predicate - by associating a function from worlds to extensions for each.
	From: Cover,J/O'Leary-Hawthorne,J (Substance and Individuation in Leibniz [1999], 2.2)
	A reaction: I take this to mean that essentialism is the view that if some predicate attaches to an object then that predicate is essential if there is an extension of that predicate in all possible worlds. In English, essential predicates are necessary predicates.

9. Objects / E. Objects over Time / 12. Origin as Essential

13101	Necessity-of-origin won't distinguish ex nihilo creations, or things sharing an origin [Cover/O'Leary-Hawthorne]
	Full Idea: A necessity-of-origins approach cannot work to distinguish things that come into being genuinely ex nihilo, and cannot work to distinguish things sharing a single origin.
	From: Cover,J/O'Leary-Hawthorne,J (Substance and Individuation in Leibniz [1999], 7.4.1)
	A reaction: Since I am deeply suspicious of essentiality or necessity of origin (and they are not, I presume, the same thing) I like these two. Twins have always bothered me with the second case (where order of birth seems irrelevant).

10. Modality / E. Possible worlds / 3. Transworld Objects / a. Transworld identity

13081	Even extreme modal realists might allow transworld identity for abstract objects [Cover/O'Leary-Hawthorne]
	Full Idea: It might be suggested that even the extreme modal realist can countenance transworld identity for abstract objects.
	From: Cover,J/O'Leary-Hawthorne,J (Substance and Individuation in Leibniz [1999], 3.2.2 n46)
	A reaction: This may sound right for uncontroversial or well-defined abstracta such as numbers and circles, but even 'or' is ambiguous, and heaven knows what the transworld identity of 'democracy' is!

14. Science / D. Explanation / 2. Types of Explanation / c. Explanations by coherence

13071	We can go beyond mere causal explanations if we believe in an 'order of being' [Cover/O'Leary-Hawthorne]
	Full Idea: The philosopher comfortable with an 'order of being' has richer resources to make sense of the 'in virtue of' relation than that provided only by causal relations between states of affairs, positing in addition other sorts of explanatory relationships.
	From: Cover,J/O'Leary-Hawthorne,J (Substance and Individuation in Leibniz [1999], 1.1.2)
	A reaction: This might best be characterised as 'ontological dependence', and could be seen as a non-causal but fundamental explanatory relationship, and not one that has to depend on a theistic world view.

27. Natural Reality / G. Biology / 3. Evolution

3804	Darwin's idea was the best idea ever [Dennett]
	Full Idea: If I were to give an award for the single best idea anyone has ever had, I'd give it to Darwin.
	From: Daniel C. Dennett (Darwin's Dangerous Idea [1995], §1.1)