Combining Texts

All the ideas for 'A Puzzle about Belief', 'What is the Source of Knowledge of Modal Truths?' and 'Understanding the Infinite'

expand these ideas     |    start again     |     specify just one area for these texts


53 ideas

2. Reason / D. Definition / 6. Definition by Essence
A definition of a circle will show what it is, and show its generating principle [Lowe]
Defining an ellipse by conic sections reveals necessities, but not the essence of an ellipse [Lowe]
An essence is what an entity is, revealed by a real definition; this is not an entity in its own right [Lowe]
2. Reason / D. Definition / 11. Ostensive Definition
Simple things like 'red' can be given real ostensive definitions [Lowe]
4. Formal Logic / F. Set Theory ST / 1. Set Theory
Second-order set theory just adds a version of Replacement that quantifies over functions [Lavine]
4. Formal Logic / F. Set Theory ST / 2. Mechanics of Set Theory / b. Terminology of ST
An 'upper bound' is the greatest member of a subset; there may be several of these, so there is a 'least' one [Lavine]
4. Formal Logic / F. Set Theory ST / 3. Types of Set / a. Types of set
Collections of things can't be too big, but collections by a rule seem unlimited in size [Lavine]
4. Formal Logic / F. Set Theory ST / 3. Types of Set / d. Infinite Sets
Those who reject infinite collections also want to reject the Axiom of Choice [Lavine]
4. Formal Logic / F. Set Theory ST / 4. Axioms for Sets / g. Axiom of Powers VI
The Power Set is just the collection of functions from one collection to another [Lavine]
4. Formal Logic / F. Set Theory ST / 4. Axioms for Sets / h. Axiom of Replacement VII
Replacement was immediately accepted, despite having very few implications [Lavine]
4. Formal Logic / F. Set Theory ST / 4. Axioms for Sets / i. Axiom of Foundation VIII
Foundation says descending chains are of finite length, blocking circularity, or ungrounded sets [Lavine]
4. Formal Logic / F. Set Theory ST / 4. Axioms for Sets / j. Axiom of Choice IX
Pure collections of things obey Choice, but collections defined by a rule may not [Lavine]
The controversy was not about the Axiom of Choice, but about functions as arbitrary, or given by rules [Lavine]
4. Formal Logic / F. Set Theory ST / 5. Conceptions of Set / c. Logical sets
The 'logical' notion of class has some kind of definition or rule to characterise the class [Lavine]
4. Formal Logic / F. Set Theory ST / 5. Conceptions of Set / e. Iterative sets
The iterative conception of set wasn't suggested until 1947 [Lavine]
The iterative conception needs the Axiom of Infinity, to show how far we can iterate [Lavine]
The iterative conception doesn't unify the axioms, and has had little impact on mathematical proofs [Lavine]
4. Formal Logic / F. Set Theory ST / 5. Conceptions of Set / f. Limitation of Size
Limitation of Size: if it's the same size as a set, it's a set; it uses Replacement [Lavine]
4. Formal Logic / F. Set Theory ST / 6. Ordering in Sets
A collection is 'well-ordered' if there is a least element, and all of its successors can be identified [Lavine]
5. Theory of Logic / A. Overview of Logic / 7. Second-Order Logic
Second-order logic presupposes a set of relations already fixed by the first-order domain [Lavine]
5. Theory of Logic / D. Assumptions for Logic / 2. Excluded Middle
Mathematical proof by contradiction needs the law of excluded middle [Lavine]
6. Mathematics / A. Nature of Mathematics / 1. Mathematics
Mathematics is nowadays (thanks to set theory) regarded as the study of structure, not of quantity [Lavine]
6. Mathematics / A. Nature of Mathematics / 3. Nature of Numbers / b. Types of number
Every rational number, unlike every natural number, is divisible by some other number [Lavine]
6. Mathematics / A. Nature of Mathematics / 3. Nature of Numbers / g. Real numbers
For the real numbers to form a set, we need the Continuum Hypothesis to be true [Lavine]
6. Mathematics / A. Nature of Mathematics / 3. Nature of Numbers / h. Reals from Cauchy
Cauchy gave a necessary condition for the convergence of a sequence [Lavine]
6. Mathematics / A. Nature of Mathematics / 3. Nature of Numbers / i. Reals from cuts
The two sides of the Cut are, roughly, the bounding commensurable ratios [Lavine]
6. Mathematics / A. Nature of Mathematics / 4. Using Numbers / c. Counting procedure
Counting results in well-ordering, and well-ordering makes counting possible [Lavine]
6. Mathematics / A. Nature of Mathematics / 5. The Infinite / a. The Infinite
The theory of infinity must rest on our inability to distinguish between very large sizes [Lavine]
The infinite is extrapolation from the experience of indefinitely large size [Lavine]
6. Mathematics / A. Nature of Mathematics / 5. The Infinite / c. Potential infinite
The intuitionist endorses only the potential infinite [Lavine]
6. Mathematics / A. Nature of Mathematics / 5. The Infinite / f. Uncountable infinities
'Aleph-0' is cardinality of the naturals, 'aleph-1' the next cardinal, 'aleph-ω' the ω-th cardinal [Lavine]
6. Mathematics / A. Nature of Mathematics / 5. The Infinite / h. Ordinal infinity
Ordinals are basic to Cantor's transfinite, to count the sets [Lavine]
Paradox: the class of all ordinals is well-ordered, so must have an ordinal as type - giving a bigger ordinal [Lavine]
6. Mathematics / A. Nature of Mathematics / 5. The Infinite / i. Cardinal infinity
Paradox: there is no largest cardinal, but the class of everything seems to be the largest [Lavine]
6. Mathematics / B. Foundations for Mathematics / 6. Mathematics as Set Theory / a. Mathematics is set theory
Set theory will found all of mathematics - except for the notion of proof [Lavine]
6. Mathematics / C. Sources of Mathematics / 1. Mathematical Platonism / b. Against mathematical platonism
Modern mathematics works up to isomorphism, and doesn't care what things 'really are' [Lavine]
6. Mathematics / C. Sources of Mathematics / 10. Constructivism / b. Intuitionism
Intuitionism rejects set-theory to found mathematics [Lavine]
9. Objects / B. Unity of Objects / 3. Unity Problems / c. Statue and clay
The essence of lumps and statues shows that two objects coincide but are numerically distinct [Lowe]
The essence of a bronze statue shows that it could be made of different bronze [Lowe]
9. Objects / D. Essence of Objects / 4. Essence as Definition
Grasping an essence is just grasping a real definition [Lowe]
9. Objects / D. Essence of Objects / 8. Essence as Explanatory
Explanation can't give an account of essence, because it is too multi-faceted [Lowe]
9. Objects / D. Essence of Objects / 14. Knowledge of Essences
If we must know some entity to know an essence, we lack a faculty to do that [Lowe]
10. Modality / A. Necessity / 3. Types of Necessity
Logical necessities, based on laws of logic, are a proper sub-class of metaphysical necessities [Lowe]
10. Modality / A. Necessity / 5. Metaphysical Necessity
'Metaphysical' necessity is absolute and objective - the strongest kind of necessity [Lowe]
10. Modality / B. Possibility / 2. Epistemic possibility
'Epistemic' necessity is better called 'certainty' [Lowe]
10. Modality / C. Sources of Modality / 6. Necessity from Essence
If an essence implies p, then p is an essential truth, and hence metaphysically necessary [Lowe]
Metaphysical necessity is either an essential truth, or rests on essential truths [Lowe]
10. Modality / E. Possible worlds / 1. Possible Worlds / e. Against possible worlds
We could give up possible worlds if we based necessity on essences [Lowe]
12. Knowledge Sources / E. Direct Knowledge / 2. Intuition
'Intuitions' are just unreliable 'hunches'; over centuries intuitions change enormously [Lowe]
18. Thought / B. Mechanics of Thought / 5. Mental Files
Puzzled Pierre has two mental files about the same object [Recanati on Kripke]
18. Thought / D. Concepts / 1. Concepts / a. Nature of concepts
A concept is a way of thinking of things or kinds, whether or not they exist [Lowe]
19. Language / B. Reference / 3. Direct Reference / a. Direct reference
Direct reference doesn't seem to require that thinkers know what it is they are thinking about [Lowe]
26. Natural Theory / D. Laws of Nature / 8. Scientific Essentialism / e. Anti scientific essentialism
H2O isn't necessary, because different laws of nature might affect how O and H combine [Lowe]