Combining Texts

All the ideas for 'Substance and Individuation in Leibniz', 'First-Order Logic' and 'Mechanism, purpose and explan. exclusion'

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21 ideas

5. Theory of Logic / A. Overview of Logic / 1. Overview of Logic

10282	Logic is the study of sound argument, or of certain artificial languages (or applying the latter to the former) [Hodges,W]
	Full Idea: A logic is a collection of closely related artificial languages, and its older meaning is the study of the rules of sound argument. The languages can be used as a framework for studying rules of argument.
	From: Wilfrid Hodges (First-Order Logic [2001], 1.1)
	A reaction: [Hodges then says he will stick to the languages] The suspicion is that one might confine the subject to the artificial languages simply because it is easier, and avoids the tricky philosophical questions. That approximates to computer programming.

5. Theory of Logic / I. Semantics of Logic / 1. Semantics of Logic

10283	A formula needs an 'interpretation' of its constants, and a 'valuation' of its variables [Hodges,W]
	Full Idea: To have a truth-value, a first-order formula needs an 'interpretation' (I) of its constants, and a 'valuation' (ν) of its variables. Something in the world is attached to the constants; objects are attached to variables.
	From: Wilfrid Hodges (First-Order Logic [2001], 1.3)

10284	There are three different standard presentations of semantics [Hodges,W]
	Full Idea: Semantic rules can be presented in 'Tarski style', where the interpretation-plus-valuation is reduced to the same question for simpler formulas, or the 'Henkin-Hintikka style' in terms of games, or the 'Barwise-Etchemendy style' for computers.
	From: Wilfrid Hodges (First-Order Logic [2001], 1.3)
	A reaction: I haven't yet got the hang of the latter two, but I note them to map the territory.

10285	I |= φ means that the formula φ is true in the interpretation I [Hodges,W]
	Full Idea: I |= φ means that the formula φ is true in the interpretation I.
	From: Wilfrid Hodges (First-Order Logic [2001], 1.5)
	A reaction: [There should be no space between the vertical and the two horizontals!] This contrasts with |-, which means 'is proved in'. That is a syntactic or proof-theoretic symbol, whereas |= is a semantic symbol (involving truth).

5. Theory of Logic / J. Model Theory in Logic / 3. Löwenheim-Skolem Theorems

10288	Down Löwenheim-Skolem: if a countable language has a consistent theory, that has a countable model [Hodges,W]
	Full Idea: Downward Löwenheim-Skolem (the weakest form): If L is a first-order language with at most countably many formulas, and T is a consistent theory in L. Then T has a model with at most countably many elements.
	From: Wilfrid Hodges (First-Order Logic [2001], 1.10)

10289	Up Löwenheim-Skolem: if infinite models, then arbitrarily large models [Hodges,W]
	Full Idea: Upward Löwenheim-Skolem: every first-order theory with infinite models has arbitrarily large models.
	From: Wilfrid Hodges (First-Order Logic [2001], 1.10)

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

10287	If a first-order theory entails a sentence, there is a finite subset of the theory which entails it [Hodges,W]
	Full Idea: Compactness Theorem: suppose T is a first-order theory, ψ is a first-order sentence, and T entails ψ. Then there is a finite subset U of T such that U entails ψ.
	From: Wilfrid Hodges (First-Order Logic [2001], 1.10)
	A reaction: If entailment is possible, it can be done finitely.

6. Mathematics / B. Foundations for Mathematics / 6. Mathematics as Set Theory / a. Mathematics is set theory

10286	A 'set' is a mathematically well-behaved class [Hodges,W]
	Full Idea: A 'set' is a mathematically well-behaved class.
	From: Wilfrid Hodges (First-Order Logic [2001], 1.6)

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 / 1. Explanation / a. Explanation

14470	Explanatory exclusion: there cannot be two separate complete explanations of a single event [Kim]
	Full Idea: The general principle of explanatory exclusion states that two or more complete and independent explanations of the same event or phenomenon cannot coexist.
	From: Jaegwon Kim (Mechanism, purpose and explan. exclusion [1989], 3)
	A reaction: This is a rather optimistic view of explanations, with a strong element of reality involved. I would have thought there were complete explanations at different 'levels', which were complementary to one another.

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.