Combining Texts

All the ideas for 'works (all lost)', 'The Metaphysics of Modality' and 'On Second-Order Logic'

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32 ideas

1. Philosophy / E. Nature of Metaphysics / 2. Possibility of Metaphysics
12027 There must be a plausible epistemological theory alongside any metaphysical theory [Forbes,G]
4. Formal Logic / B. Propositional Logic PL / 2. Tools of Propositional Logic / a. Symbols of PL
12005 The symbol 'ι' forms definite descriptions; (ιx)F(x) says 'the x which is such that F(x)' [Forbes,G]
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]
10830 Second-order logic metatheory is set-theoretic, and second-order validity has set-theoretic problems [Boolos]
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]
5. Theory of Logic / E. Structures of Logic / 2. Logical Connectives / d. and
12010 Is the meaning of 'and' given by its truth table, or by its introduction and elimination rules? [Forbes,G]
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]
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]
5. Theory of Logic / K. Features of Logics / 6. Compactness
13841 Why should compactness be definitive of logic? [Boolos, by Hacking]
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]
7. Existence / D. Theories of Reality / 10. Vagueness / d. Vagueness as linguistic
12023 Vagueness problems arise from applying sharp semantics to vague languages [Forbes,G]
9. Objects / A. Existence of Objects / 5. Individuation / a. Individuation
12017 In all instances of identity, there must be some facts to ensure the identity [Forbes,G]
9. Objects / B. Unity of Objects / 3. Unity Problems / d. Coincident objects
12024 If we combined two clocks, it seems that two clocks may have become one clock. [Forbes,G]
9. Objects / D. Essence of Objects / 3. Individual Essences
11885 Only individual essences will ground identities across worlds in other properties [Forbes,G, by Mackie,P]
12014 An individual essence is a set of essential properties which only that object can have [Forbes,G]
12015 Non-trivial individual essence is properties other than de dicto, or universal, or relational [Forbes,G]
9. Objects / D. Essence of Objects / 5. Essence as Kind
12013 Essential properties depend on a category, and perhaps also on particular facts [Forbes,G]
9. Objects / D. Essence of Objects / 7. Essence and Necessity / a. Essence as necessary properties
12012 Essential properties are those without which an object could not exist [Forbes,G]
9. Objects / D. Essence of Objects / 11. Essence of Artefacts
12025 Artefacts have fuzzy essences [Forbes,G]
12022 Same parts does not ensure same artefact, if those parts could constitute a different artefact [Forbes,G]
9. Objects / E. Objects over Time / 12. Origin as Essential
12020 An individual might change their sex in a world, but couldn't have differed in sex at origin [Forbes,G]
9. Objects / F. Identity among Objects / 1. Concept of Identity
11888 Identities must hold because of other facts, which must be instrinsic [Forbes,G, by Mackie,P]
10. Modality / A. Necessity / 4. De re / De dicto modality
12003 De re modal formulae, unlike de dicto, are sensitive to transworld identities [Forbes,G]
10. Modality / C. Sources of Modality / 4. Necessity from Concepts
12028 De re necessity is a form of conceptual necessity, just as de dicto necessity is [Forbes,G]
10. Modality / E. Possible worlds / 1. Possible Worlds / c. Possible worlds realism
12008 Unlike places and times, we cannot separate possible worlds from what is true at them [Forbes,G]
12009 The problem with possible worlds realism is epistemological; we can't know properties of possible objects [Forbes,G]
10. Modality / E. Possible worlds / 2. Nature of Possible Worlds / a. Nature of possible worlds
12007 Possible worlds are points of logical space, rather like other times than our own [Forbes,G]
10. Modality / E. Possible worlds / 3. Transworld Objects / a. Transworld identity
12011 Transworld identity concerns the limits of possibility for ordinary things [Forbes,G]
12016 The problem of transworld identity can be solved by individual essences [Forbes,G]
10. Modality / E. Possible worlds / 3. Transworld Objects / c. Counterparts
12004 Counterpart theory is not good at handling the logic of identity [Forbes,G]
10. Modality / E. Possible worlds / 3. Transworld Objects / d. Haecceitism
12021 Haecceitism attributes to each individual a primitive identity or thisness [Forbes,G]
12029 We believe in thisnesses, because we reject bizarre possibilities as not being about that individual [Forbes,G]