15 ideas
| 23623 | Predicativism says only predicated sets exist [Hossack] |
| Full Idea: Predicativists doubt the existence of sets with no predicative definition. | |
| From: Keith Hossack (Knowledge and the Philosophy of Number [2020], 02.3) | |
| A reaction: This would imply that sets which encounter paradoxes when they try to be predicative do not therefore exist. Surely you can have a set of random objects which don't fall under a single predicate? |
| 23624 | The iterative conception has to appropriate Replacement, to justify the ordinals [Hossack] |
| Full Idea: The iterative conception justifies Power Set, but cannot justify a satisfactory theory of von Neumann ordinals, so ZFC appropriates Replacement from NBG set theory. | |
| From: Keith Hossack (Knowledge and the Philosophy of Number [2020], 09.9) | |
| A reaction: The modern approach to axioms, where we want to prove something so we just add an axiom that does the job. |
| 23625 | Limitation of Size justifies Replacement, but then has to appropriate Power Set [Hossack] |
| Full Idea: The limitation of size conception of sets justifies the axiom of Replacement, but cannot justify Power Set, so NBG set theory appropriates the Power Set axiom from ZFC. | |
| From: Keith Hossack (Knowledge and the Philosophy of Number [2020], 09.9) | |
| A reaction: Which suggests that the Power Set axiom is not as indispensable as it at first appears to be. |
| 23628 | The connective 'and' can have an order-sensitive meaning, as 'and then' [Hossack] |
| Full Idea: The sentence connective 'and' also has an order-sensitive meaning, when it means something like 'and then'. | |
| From: Keith Hossack (Knowledge and the Philosophy of Number [2020], 10.4) | |
| A reaction: This is support the idea that orders are a feature of reality, just as much as possible concatenation. Relational predicates, he says, refer to series rather than to individuals. Nice point. |
| 23627 | 'Before' and 'after' are not two relations, but one relation with two orders [Hossack] |
| Full Idea: The reason the two predicates 'before' and 'after' are needed is not to express different relations, but to indicate its order. Since there can be difference of order without difference of relation, the nature of relations is not the source of order. | |
| From: Keith Hossack (Knowledge and the Philosophy of Number [2020], 10.3) | |
| A reaction: This point is to refute Russell's 1903 claim that order arises from the nature of relations. Hossack claims that it is ordered series which are basic. I'm inclined to agree with him. |
| 14620 | Theories in logic are sentences closed under consequence, but in truth discussions theories have axioms [Fine,K] |
| Full Idea: It is customary in logic to take a theory to be a set of sentences closed under logical consequence, whereas it is common in discussions of theories of truth to take a theory to be an axiomatized theory. | |
| From: Kit Fine (Semantic Necessity [2010], n8) |
| 23626 | Transfinite ordinals are needed in proof theory, and for recursive functions and computability [Hossack] |
| Full Idea: The transfinite ordinal numbers are important in the theory of proofs, and essential in the theory of recursive functions and computability. Mathematics would be incomplete without them. | |
| From: Keith Hossack (Knowledge and the Philosophy of Number [2020], 10.1) | |
| A reaction: Hossack offers this as proof that the numbers are not human conceptual creations, but must exist beyond the range of our intellects. Hm. |
| 23621 | Numbers are properties, not sets (because numbers are magnitudes) [Hossack] |
| Full Idea: I propose that numbers are properties, not sets. Magnitudes are a kind of property, and numbers are magnitudes. …Natural numbers are properties of pluralities, positive reals of continua, and ordinals of series. | |
| From: Keith Hossack (Knowledge and the Philosophy of Number [2020], Intro) | |
| A reaction: Interesting! Since time can have a magnitude (three weeks) just as liquids can (three litres), it is not clear that there is a single natural property we can label 'magnitude'. Anything we can manage to measure has a magnitude. |
| 23622 | We can only mentally construct potential infinities, but maths needs actual infinities [Hossack] |
| Full Idea: Numbers cannot be mental objects constructed by our own minds: there exists at most a potential infinity of mental constructions, whereas the axioms of mathematics require an actual infinity of numbers. | |
| From: Keith Hossack (Knowledge and the Philosophy of Number [2020], Intro 2) | |
| A reaction: Doubt this, but don't know enough to refute it. Actual infinities were a fairly late addition to maths, I think. I would think treating fictional complete infinities as real would be sufficient for the job. Like journeys which include imagined roads. |
| 14530 | The role of semantic necessity in semantics is like metaphysical necessity in metaphysics [Fine,K, by Hale/Hoffmann,A] |
| Full Idea: Fine's paper argues that the notion of semantic necessity has a role to play in understanding the nature and content of semantics comparable to the role of metaphysical necessity in metaphysics. | |
| From: report of Kit Fine (Semantic Necessity [2010]) by Bob Hale/ Aviv Hoffmann - Introduction to 'Modality' 2 |
| 3102 | Why don't we experience or remember going to sleep at night? [Magee] |
| Full Idea: As a child it was incomprehensible to me that I did not experience going to sleep, and never remembered it. When my sister said 'Nobody remembers that', I just thought 'How does she know?' | |
| From: Bryan Magee (Confessions of a Philosopher [1997], Ch.I) | |
| A reaction: This is actually evidence for something - that we do not have some sort of personal identity which is separate from consciousness, so that "I am conscious" would literally mean that an item has a property, which it can lose. |
| 14618 | Semantics is either an assignment of semantic values, or a theory of truth [Fine,K] |
| Full Idea: On one view, a semantics for a given language is taken to be an assignment of semantic values to its expressions; according to the other, a semantics is taken to be a theory of truth for that language. | |
| From: Kit Fine (Semantic Necessity [2010], Intro) | |
| A reaction: The first is Frege, the second Tarski via Davidson, says Fine. Fine argues against these as the correct alternatives, and says the distinction prevents us understanding what is really going on. He votes for semantics as giving 'semantic requirements'. |
| 14621 | Semantics is a body of semantic requirements, not semantic truths or assigned values [Fine,K] |
| Full Idea: Semantics should be conceived as a body of semantic requirements or facts - and not as a body of semantic truths, or as an assignment of semantic values. | |
| From: Kit Fine (Semantic Necessity [2010], 5) | |
| A reaction: The 'truths' view is Tarski, and the 'values' view is Frege. You'll have to read the Fine paper to grasp his subtle claim. |
| 14622 | Referential semantics (unlike Fregeanism) allows objects themselves in to semantic requirements [Fine,K] |
| Full Idea: What distinguishes the referential position in semantics from Fregeanism is that it makes use of de re semantic facts, in which it is required of an object itself that it enter into certain semantic requirements. | |
| From: Kit Fine (Semantic Necessity [2010], 5) | |
| A reaction: I have a repugnance to any sort of semantics that involves the objects themselves, even when dealing with proper names. If I talk of 'Napoleon', no small Frenchman is to be found anywhere in my sentences. |
| 14619 | The Quinean doubt: are semantics and facts separate, and do analytic sentences have no factual part? [Fine,K] |
| Full Idea: The source of the Quinean scepticism about analytic and synthetic is, first, scepticism over whether we can factor truth into a semantic and a factual component, and (second) if we can, is the factual component ever null? | |
| From: Kit Fine (Semantic Necessity [2010], 1) | |
| A reaction: You certainly can't grasp 'bachelors are unmarried men' if you haven't grasped the full Woosterian truth about men and marriage. But I could interdefine four meaningless words, so that you could employ them in analytic sentences. |